Christmas Geobaubles 2020

Merry Christmas! Now in its 5th year, here are 2020’s Geobaubles to bring you some Christmas cheer!

This year’s baubles are photomicrographs of mineral pigments under the microscope in plane-polarised and cross-polarised light. Clockwise from top left they are: crocoite, manganese violet, verditer (synthetic azurite), asbestos (chrysotile) and in the centre, realgar.

For best effect, print off two sheets, out out the shapes and glue them back-to-back to attain all-round petrology glamour!

Previous year’s Geobaubles are available at …

Christmas 2019

Christmas 2018

Christmas 2016 & 2017

Geobaubles 2019

Here they are, petrological themed Christmas decorations for December 2019! This year we have (clockwise from top left) a green schist from the Cyclades, a basalt from Santorini, peridotite from Oman and essexite from Crawfordjohn, Scotland. The star is shonkinite from Shonkin Sag. Enjoy! Do post pictures of your geobaubles in use on Twitter (tag @R_Siddall) or Instagram  (@ruthie.siddall) and use the hashtag #geobaubles2019

For best effect, print off two sheets, out out the shapes and glue them back to back to attain all-round petrology glamour!

Merry Christmas!

Previous year’s Geobaubles are available here:

Christmas 2018

Christmas 2016 & 2017

 

Blushing Minerals

Whilst visiting the Church of St Eleth’s Church in Amlwch, Anglesey to look at its construction and building materials, my eye was caught by an interesting grave slab in Cambrian slate from the Welsh mainland. It commemorates an early mine ‘geologist’, Jonathan Roose who worked at the copper mines at Parys Mountain nearby.

Jonathan Roose died in the 6^thFebruary 1815, aged a venerable 85 years. He was buried in the churchyard of St Eleth’s in Amwch. He is one of the reputed discoverers of the copper ores at Parys Mountain in north Anglesey. These deposits of chalcopyrite-rich ore were huge in the 18^thand 19^thCenturies where they were exploited and used in the ship-building industry for ‘copper-bottomed boats. According to historical sources, the ore was discovered in 1768 by a Rowland Pugh (who was subsequently awarded a bottle of whisky). The Parys Mine Company was founded in 1774 when Jonathan Roose was employed as the ‘technical consultant’. Almost certainly he was responsible for the discovery or numerous further deposits, as his eulogy suggests. The operation of copper extraction and smelting at Porth Amlwch was huge; 3 million tonnes of ore was converted into 130 thousand tonnes of copper between 1788 and 1805.

From the graves of the Roose family in St Eleth’s churchyard, there was clearly a tradition for poetic eulogies to be inscribed onto gravestones, though Jonathan gets the longest poem. Perhaps a family member fancied themselves as a poet (probably to the horror of the memorial mason’s letter cutter). Do not expect great art here!

Among this throng of congregated dead,
Of kindred men whose spirits hence are fled,
Here lieth one whose mind had long to bear,
A toilsome task of industry and care.
He first yon Mountain’s wondrous riches found,
First drew its minerals blushing from the ground,
He heard the miners’ first exciting shout,
Then toil’d near Fifty Years to guide its treasures out. 

The course of time will soon this stone decay,
His name, his memory will pass away,
Yet shall be left some monuments behind,
The mighty products of his master-mind,
Those labour’d levels which he formed to draw,
The teemful waters to the vale below,
And pillar’d caverns whence he drew the ores,
Will long his genius shew – when known his name no more.

Pugh’s and Roose’s discoveries were in fact rediscoveries. Archaeological excavations at Parys Mountain have revealed Bronze Age hammer stones suggesting copper was mined here as early as 2000 BCE, perhaps one of the first copper mines in the British Isles. The Romans also worked copper here, leaving copper cakes with stamped inscriptions. The ore itself is a kuroko-type deposit volcanic massive sulphides.

Further Reading
Barrett, T. J., MacLean, W. H. & Tennant, S. C., 2001, Volcanic Sequence and Alteration at the Parys Mountain Volcanic-Hosted Massive Sulfide Deposit, Wales, United Kingdom: Applications of Immobile Element Lithogeochemistry., Economic Geology, 96, 1279-1305.

Jenkins, D.A. 1995. Mynydd Parys Copper Mines. Archaeology in Wales 35: 35–37.

Timberlake, S. & Marshall, P., 2018, Chapter 29. Copper mining and smelting in the British Bronze Age: new evidence of mine sites including some re-analysis of dates and ore sources., in: Ben-Yosef, E. (Ed)., Mining for Ancient Copper Essays in Memory of Beno Rothenberg., Eisenbrauns: Winona Lake, Indiana and Emery and Claire Yass Publications in Archaeology: Tel Aviv University, 418-431.

Parys Mountain, Amlwch; Casgliad y Werin Cymru/People’s Collection Wales

Field notes on some Broadland churches in the Wroxham area, Norfolk

Field notes on some Broadland churches in the Wroxham area, Norfolk.

Ruth Siddall, January 2019.

 The building stones of Broadland Churches visited by Ruth Siddall and Tim Atkinson on 12 January 2019. Please regard these as field notes; they are not intended to be exhaustive or complete records of the fabric of the churches described below. 

St Peter’s, Belaugh

TG 2890 1841

12^thCentury with 15^thCentury alterations and 19^thCentury restoration by Butterfield & Phipson.

Rubble Masonry: Coarse flint, ferricrete, Wroxham Crag[1]component (minor), beach flints (minor).

Course flints retain cortices and may be very large > 30 cm long-axis single flints (NB very large flints are also used as gate posts in the village).

Ferricrete (very dark brown – almost black, pebbly [angular, moderately sorted], friable and rarer pieces of rust-red pebbly variety, with stratified pebbles). The dark ferricrete is used for quoins on NE corner and for (filled) window dressings on the north wall and as squared blocks in the lower part of this wall. These are probably from the 12^thCentury phase and the ferricretes blocks are possibly reused. Ferricrete blocks have developed a pale green-white encrusting limestone.

Wroxham Crag component: white vein quartz cobble (south wall, close to door).

15^thCentury rubble masonry includes a few slabs of Barnack Stone on west wall. Clipsham Stone dressings on windows of this period?

19^thCentury – Knapped flint work with Ancaster Stone dressings. Uncoursed, coarse flint with cortices. Some Conulussp. echinoids. Some coursed, square-knapped flint work on buttresses.

Interior: Font (12^thCentury) – grey green, fine grained limestone with a few white bivalve fossils. Unidentified stone.

North facing wall of St Peter’s Church, Belaugh showing several phases of construction and restoration and the distinctive, almost black blocks of ferricrete.

Knapped flints from the south facing wall containing a Conulus sp. Echinoid.

Blocks of ferricrete along with unknapped, uncoursed flints in the south wall of St Peter’s Church, Belaugh. These stones have been recycled into restoration phases.

Ferricrete used as quoins and ashlar on the NE corner of the church.

 

St Helen’s, Ranworth

Woodbastwick Road, Ranworth, Norfolk NR13 6HS

TG 3560 1476

First phase 1290-1350, Second Phase (Perpendicular-style alterations) up to 1530. Rood Screen 1419. North side of the church is much colonised by lichen.

Carved plinths (lamb of God, shields) on buttresses – Clipsham or possibly Barnack Stone.

Quoins, tracery and other dressings: Clipsham Stone

Rubble Masonry: Coarse flint, ferricrete (bright red-orange), Greensand (minor), Wroxham Crag component (vein quartz, Triassic quartzites, chatter-marked flints).

Flints – coarse with intact cortices, some knapped. Probably some are field flints. Upper parts of the building, including the tower have a large amount of red-orange flints. A circular, red flint in the tower (south side, c. 12 m up) is a paramoudra. Square, knapped, coursed flint work on foundations and buttresses.

Red-stained flints on the tower at St Helen’s, Ranworth including a ring-shaped paramoudra from the local chalk

Red-stained flint with fossil echinoid.

Ferricrete is a bright orange red cemented gravel with rounded to sub-rounded, poorly sorted, flint pebbles up to 4 cm long axis. Some blocks are of a gritty sand with sparse pebbles.

Blocks of ferricrete at St Helen’s Church, Ranworth.

The ferricrete has variable texture and clast size/distribution. However, it is notably a bright. Brick red in colour.

Wroxham Crag component: cobbles of vein quartz and red-pink Triassic Bunter pebbles (fist size) are common within the fabric, as are rounded, chatter-marked beach flints.

   Vein quartz cobbles from the Wroxham Crag at St Helen’s, Ranworth.

Spolia: a few rough fragments of Barnack Stone and a fine-grained Caen Stone pilaster. Greensands (possibly Kentish Rag) occur in a few squared blocks. These are possibly spolia or ballast.

Small pillar of Caen Stone spolia.

Greensand block, probably spolia or ballast.

Interior: grave slab of Green Purbeck Marble (with Uniosp.) flanked by smaller slabs of Red Purbeck Marble. Also slabs of 18^thCentury of black Lower Carboniferous limestone with small white rugose corals, sparse brachiopods and a gastropod. This is probably Belgian or Irish in origin.

 Green Purbeck Marble grave slab with thick walled, Unio sp. Bivalves inside St Helen’s Church, Ranworth.

 

St Mary’s, South Walsham

23, The Street, South Walsham NR13 6DQ

TG 3653 1325

First phase 12^th-13^thCentury but much is 13^th-14^thCentury. Tower and porch are 15^thCentury. Heritage Norfolk states ‘This church has a large quantity of lava incorporated into the walls along with reused masonry.’ I have no idea what the ‘lava’ refers to!

Lower courses (C12-13) of coarse flints with cortices intact, roughly coursed. Upper parts of knapped, uncoursed flint with spolia. The latter is composed of slabs of Purbeck Marble (much weathered, but with clear Viviparussp., 10 cm thick, c. 30 cm long) occur about 1 m up from foundations in the south and east chancel walls. Also, a fragment of carved, spoliated capital in Caen Stone or Clunch to the west of the down pipe of the buttress between the nave and chancel on the south side.

Exotic pebbles: sub-angular, brown, quartz arenites. These may be derived from the Crag or tills or could be ballast. Possibly striation on one example suggests till.

Porch: Square knapped, coursed flint flushwork with Clipsham Stone dressings (15^thCentury).

Unknapped, beach flints have been added to the top of the walls of the north porch, probably in in the 19^thCentury.

Knapped, coarse flints with boulders of brown arenaceous sandstone at St Mary’s, South Walsham.

The photo above shows a boulder which may show evidence of glacial striae.

St Mary’s Church, South Walsham. Fragment of carved capital in Caen Stone used as spolia in the church’s fabric.

Slabs of Purbeck stone, weathering in are laid in a line across the centre of the photograph.

 

St Lawrence’s, South Walsham

The Street, South Walsham NR13 6DQ, located next door to St Mary’s (above)

A 14^thCentury Church restored in 1992. This building was visited very briefly.

Knapped, uncoursed flint work with Clipsham Stone dressings.

Stonework at St Lawrence’s, South Walsham; detail of Clipsham Stone dressings; this cross-bedded calcarenite is packed with shell fragments.

Knapped flint cobbles.

 

All Saints, Hemblington

Church Lane NR13 4EF

TG 35 11

Saxon-Norman Round Tower, chancel c. 1300, nave c. 1400 with 15^thCentury roof and wall-paintings (of St Christopher).

Walls are predominantly of unknapped, coursed flint with cortices intact. Some (faint) herringbone coursing. Some knapped flint.

Exotic cobbles: Abundant, well-rounded quartzite (Triassic) pebbles and also sub-rounded to sub-angular cobbles of brown arenaceous sandstones, probably from Wroxham Crag and related deposits. Also a few one-off finds i.e. Hertfordshire Puddingstone sarsen, a medium-grained diorite.

Abundant spolia in Caen Stone is present. The Tudor brick window on the tower is cut into what was probably a spoliated window sill in Caen Stone. There is also a large amount of brick and tile incorporated into the walls.

Flushwork, knapped flint crosses on either side of the south porch entrance.

Dressings on buttresses in Lincolnshire Limestone (not fully observed).

The east end of All Saints Church, Hemblington showing at least two phases of construction.

Flushwork flint crosses in the brick-built south porch.

Carved spolia and rough flints in the walls.

Carved spolia in Caen stone. This is the remains of a window sill which has been cut into by Tudor brick work (on the left of the image).

Detail of stones at All Saints Church, Hemblington. Triassic quartzite split pebble.

A medium grained diorite of unknown origin.

Hertfordshire puddingstone, a form of sarsen.

Knapped flint with the trace of a fossil echinoid.

Download these notes as a pdf

Bibliography

Candy, I., Lee, J. R. & Harrison, A. M. (Eds.), 2008, The Quaternary of northern East Anglia., Quaternary Research Association., 263 pp.

Hart, S., 2000, Flint architecture of East Anglia., Giles de la Mare Publishers Ltd., London., 150 pp.

Norfolk Heritage Explorer

[1]According to Candy et al. (2008), the pre-Anglian Wroxham Crag and associated Bytham Gravel Beds contain a clastic component dominated by pebbles and cobbles of vein quartz, Triassic quartzite, ‘schorl’, Carboniferous chert, RhaxellaChert, flint and chatter-marked flint. The Bytham River flowed from the English Midlands, eastwards into the North Sea and provided a sediment source for the Wroxham Crag. The Wroxham Crag is differentiated from the underlying Norwich Crag by the presence of these ‘far travelled pebbles’.

Christmas Geobaubles 2018

Here are my thin section Christmas geobaubles for 2018!

For festive geologically themed decorations, print off two sheets, cut out the baubles and stick the two sides together. Pierce the black hole in the tag to thread a string.

Merry Petrological Christmas Everyone!

Ruth  xxxx

Previous year’s #geobaubles

Urban Geology New Year Quiz 2017

This quiz was first posted on Twitter over the New Year Weekend of 2017-2018. If you missed it, both questions and answers are given here. Scroll down for answers.

 

Q1. Where do these coloured marbles come from?

A. Tuscany, Italy

B. Derbyshire, England

C. Devon, England

D. Namur, Belgium

 

Q2. Which is the main building stone of the British Museum?

A. Bath Stone

B. Lincolnshire Limestone

C. Portland Stone

 

Q3. This well known building stone is a rapakivi granite called Baltic Brown. Where is it quarried?

A. Denmark

B. Estonia

C. Finland

D. Sweden

 

Q4. When were the Carrara Marble quarries first worked?

A. Neolithic

B. Roman Period

C. Renaissance

D. 19^th Century

 

Q5. This is a very well-known building stone called Larvikite because its found in Larvik, Norway. Noted for its iridescent feldspars, what kind of rock is it?

A. Granite

B. Syenite

C. Monzonite

D. Gabbro

 

Q6. What type of granite is this?

A. Rubislaw Granite

B. Shap Granite

C. Dartmoor Granite

D. Sardinian Granite

 

Q7. These two stones have been used on the Titanic and for St Peter’s Throne in the Vatican. In which mountain range are they quarried?

A. Atlas Mountains

B. Betics

C. Pyrenees

D. Alps

 

Q8. This fossiliferous stone is currently very fashionable, used for exterior cladding as well as paving in malls and stations. Where is it from?

A. Paris Basin

B. French Jura

C. Bavarian Jura

D.Portland Dorset

 

Q9. These two porphyries were the main stones used in a Medieval paving technique called ‘Cosmati Work’. At the time they were looted from Roman ruins, but where were they originally quarried?

A. Italy and France

B. France and Turkey

C. Turkey and Greece

D. Greece and Egypt

 

Q10. How much granite was used in the construction of London’s Victoria Embankment?

A. 500,000 m3

B. 1 million m3

C. 1.5 million m3

D. 2 million m3

 

 

Answers

Q1: Devon, England.

These colourful limestones were quarried around Torquay, Plymouth and Ashburton in Devon and were popularly used for decorative items made by the English pietra dura industry during the 19^th Century. The black limestone in which they were set is from Derbyshire.

So called ‘Devon Marbles’ were worked small-scale from the Frasnian-Givetian age Tamar Group Limestones of south Devon. You can find out more about the geology of these stones and there use in decorative works in Gordon Walkden’s books published by the Geologists’ Association.

Walkden, G., 2015, Devonshire Marbles: their geology, history and uses. Volume 1. Understanding the marbles. Geologists’ Association Guide no. 72., The Geologists’ Association, London.,1-232.

Walkden, G., 2015, Devonshire Marbles: their geology, history and uses. Volume 2. Recognising the marbles. Geologists’ Association Guide no. 72., The Geologists’ Association, London., 233-484.

 

Q2. Portland Stone.

Like many of London’s great civic buildings of the 18^th and 19^th Centuries, The British Museum is built from Upper Jurassic Portland Stone. Find out more on London Pavement Geology.

Bath Stone and Lincolnshire Limestone are also important British, Jurassic, oolitic limestones which are important building stones, however, the introduction of Portland Stone after the Great Fire of London in 1666 eclipsed their use in the capital.

 

Q3. Finland

This stone is quarried from the enormous Vyborg (Wiborg) Batholith which straddles the Finnish-Russian border. The stone shown in the photo and exported globally is quarried in Finland from several quarries near Lappeenranta in the SE of the country. It is a variety of rapakivi granite (‘rapakivi’ is a Finnish word meaning rotten rock) called a wiborgite. This rock has the distinctive ‘ovoid’ zoned feldspar megacrysts. Find out more in Axel Muller’s article in Geology Today.

Müller, A., 2007, Rocks Explained 1: Rapakivi Granites., Geology Today, 23 (3), 114-120.

 

Q4. Roman Period

Although it is probably the case that pre-Roman societies used field stones from the Massa e Carrara region for small scale use, ‘quarrying’ as we understand that term today began during the Roman period. The Romans quarried several marbles from the Carrara region including the white variety which they called ‘Luna’.

 

Q5. Monzonite

Larvikite is a monzonite, a plutonic igneous rock containing no (or very minor) quartz and equal amounts of plagioclase and K-feldspar. The iridescent (‘schillerescent’) feldspars are antiperthites with an oligoclase host and K-feldspar blebs. Find out more about the geology and use of this famous building stone here:

Heldal, T., Meyer, G. B. & Dahl, R., 2014, Global stone heritage: Larvikite, Norway., in: Pereira, D., Marker, B. R., Kramar, S., Cooper, B. J. & Schouenborg, B. E. (eds) Global Heritage Stone: Towards International Recognition of Building and Ornamental Stones. Geological Society, London, Special Publications, 407, 14 pp.

 

Q6. Dartmoor Granite

This is ‘Giant Granite’ from Dartmoor, so-called because of the large megacrysts present in this rock. There are several ‘megacrystic’ granites used in the building stone trade because they are both strong and decorative. A ‘megacryst’ is a phenocryst in a granite which is bigger than 1-2 cm. The megacrysts in Dartmoor ‘Giant Granite’ can be 10-15 cm long. Rubislaw Granite (from Aberdeen) does not contain megacrysts. Shap Granite and some varieties of Sardinian Granite are megacrystic, but usually the megacryst are on the small size. The give-away here are the lace-like blobs of black tourmaline which is characteristic of the Dartmoor Granite facies quarried around Princeton and elsewhere in the north of the pluton. The example in the photos is from Fishmongers’ Hall in London.

 

Q7. Pyrenees

A number of very decorative tectonic breccias have been quarried in the Pyrenees since the Roman period. Shown here is the pink-grey variety Sarrancolin which was used in the dining room of the Titanic (designed by Charles Fitzroy Doll who also designed the Russell Hotel, where this stone is also used). The black and white stone is generally called Grand Antique. It was first quarried by the Romans and has been worked on and off since. The quarries have recently been brought back into production by Carrieres Plo. This stone has been much favoured by the Catholic Church. It is used for the plinth of the statue of St Peter Enthroned in the Vatican and this statue (including the stones used) has been much replicated.

 

Q8. Bavarian Jura

This stone is known as ‘Jura Marble’ in the building trade. Geologically it is from the Kimmeridgian Treuchtlingen Formation and it is quarried in the Altmühltal Naturpark, Southern Frankonian Alb, Bavaria, Germany.

 

Q9. Greece and Egypt

The green porphyry is called Lapis Lacedaemonium and it was quarried near the village of Krokeai near Sparta (Spartí), Greece. This is an altered Triassic basalt. It was worked from the Bronze Age until the Byzantine Period (5^th Century AD).

The purple porphyry is the ‘original’ porphyry, named by the Romans because of its colour. It comes from the Roman Quarries of Mons Porphyrites in the Eastern Desert of Egypt which were in operation from (probably) the 3^rd Century BC to the 5^th Century AD. The rock is an andesite from the Neoproterozoic Dokhan Volcanics. It contains the epidote mineral piedmontite which is partially responsible for imparting the purple colouration.

 

Q10. 500,000 m3

Did you get lucky here? Half a million metres cubed of granite were used in embanking the Thames, the bulk of the material used was earth to backfill the new land reclaimed from the river.

Surprisingly little is written about this incredible feat of engineering. Find out more here:

Siddall, R. & Clements, D., 2015, Never in the field of urban geology have so many granites been looked at by so few! A stroll along the Victoria Embankment from Charing Cross to Westminster & Blackfriars Bridge., Urban Geology in London No. 21, 19 pp.

 

How did you do?

 >8/10 You are a building stone expert! But here’s a #toptip – don’t give up your day job!

5-8/10 Pretty good! You have some sound stone skills!

3-5/10 OK, but definitely room for improvement …

< 3/10 Better luck next time!

 

Happy New Year and thanks for participating the #UrbanGeologyQuiz!

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Christmas Geobaubles 2017

Here are my thin section Christmas geobaubles for 2017.

For festive geologically themed decorations, print off two sheets, cut out the baubles and stick the two sides together. Pierce the black hole in the tag to thread a string.

Merry Petrological Christmas Everyone!

Ruth  xxxx

 

PS Here are last years (2016) Geobaubles

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Tyndall Stone: An Iconic Canadian Building Stone

Tyndall Stone is one of Canada’s iconic building stones. Derived from near Garson, Manitoba, it is used in a great number of buildings in Winnipeg. However it shows up all over the place as a high quality and attractive stone, suitable for both exterior and interior use with honed, bush-hammered or a polished surface. With a compressive strength of 62.8 MPa, it is a very strong and durable construction limestone.

Tyndall Stone-clad portico of the Fairmont Chateau Lake Louise in Banff National Park, Alberta

Tyndall Stone is extracted from the Selkirk Formation of the Red River Group of the Williston Basin. Tyndall Stone is quarried at Gillis Quarry in south western Manitoba, but extends westwards into Saskatchewan where the lateral equivalent is known as the Yeoman Formation. These formations are overlain by evaporite deposits. Gillis Quarry exposes a 43 m thick unit of massive, metre-thick beds and have allowed excellent exposures for 3D scientific study of this stone. The rock is of Upper Ordovician (Katian, 445-453 Ma) age.

The Gillis Quarry is located around 40 km northeast of Winnipeg (see Google Maps). Most sources seem to agree that the first use of this stone was at Lower Fort Garry built in the 1830s. Gillis Quarries were brought into commercial production in 1910 and have remained in the same family ever since. The stone lends itself well to both traditional and modernist architectural styles, with finishes ranging from rough, quarry-dressed blocks to smooth, honed or polished ashlars.

Tyndall Stone is a limestone, but with a significant dolomite content.

The most striking thing about this stone – and its main decorative feature – is that it is pervasively riddled with Thalassinoides trace fossils. These are branching burrows, with T- or Y-shaped junctions made by creatures tunnelling through the soft sediment, which are typically 1 to 2.5 cm wide. These show up brown in contrast to the cream-coloured limestone matrix, this is because the burrows backfilled with dolomite. It is not known what made these burrows during the Upper Ordovician, but modern Thalassinoides burrows are made by the shrimp Callianassa so a similar crustacean is a reasonable guess (Jin et al., 2012).

Thalassinoides burrows. Tyndall Stone Cladding on the Terminal City Club, Vancouver.

Weathered Thalassinoides burrows at the Fairmont Banff Springs Hotel.

Many other fossils are present and abundant in these strata and have been described by Jin et al. (2012). The Receptaculitid Fisherites reticulatus (Finney & Nitecki, 1979) is a spectacular component of this rock, and if it were needed, a distinguishing feature of Tyndall Stone. Up to 25 cm or so in diameter, these are circular fossils with a scaly appearance, appearing like the seed head of a sunflower. They are assumed to be fossilised calcareous algae.

Fisherites at the Terminal City Club (West Cordova Street facade) in Vancouver

Fisherites on the Terminal City Club in Vancouver

A section through Fisherites on the terrace at the Fairmont Banff Springs Hotel

Also present are very large Nautiloids. These include orthocones as thick as my arm and indeed called Armenoceras. This genus along with Endoceras can be over a metre in length.

Large orthoceras sections on book matched slabs at the Fairmont Chateau Lake Louise

Orthoceras on the terrace of the Fairmont Banff Springs Hotel

The coiled Nautiloid Wilsonoceras which can reach diameters of 40 cm is also present.

Section through the chambers of a coiled Nautilus

Section through a coiled Nautilus

These cephalopods are diagnostic of the so-called ‘Arctic Cephalopod Fauna’ and are typical of these late Ordovician carbonate platforms.

Other molluscs include gastropods, such as the planispiral Maclurina and the cone-spiralled Hormotoma.

Tyndall Stone with Thalassinoides at the Fairmont Chateau Lake Louise. A possible planispiral gastropod can be seen at bottom right.

Sections through a gastropod on slabs paving the lobby of the Fairmont Banff Springs Hotel

Corals are also present. This is probably the tabulate coral Catenipora.

Fairmont Chateau Lake Louise

Rugose corals include the varieties Grewingkia, Crenulites and Palaeophyllum.

Rugose Coral on the Terminal City Club, Vancouver

Other reef-forming organisms in addition to corals and Receptaculitids are stromatoporoids of which I found only fragments.

A fragment of a stromatoporoid at the Fairmont Chateau Lake Louise

The Tyndall Stone-type of Thalassinoides facies is regionally widespread throughout the Upper Ordovician strata of Laurentia, with very similar formations existing in Greenland (Børglum River Formation), as well as in Canada and the USA (i.e. Bighorn Dolomite of Wyoming; see Jin et al., 2012; Gingras et al., 2004; Sheehan & Schiefelbein, 1984).

As a good quality freestone, Tyndall Stone has also been used for carving by a number of artists and it even gets a mention in literature. Canadian author Carol Shields described Tyndall Stone in her, perhaps predictably titled, novel ‘The Stone Diaries’; “Some folks call it tapestry stone, and they prize, especially, its random fossils: gastropods, brachiopods, trilobites, corals and snails. As the flesh of these once-living creatures decayed, a limey mud filled the casings and hardened to rock”

Urban Geology guides and descriptions of Tyndall stone buildings in Winnipeg are available by Thorsteinson (2013) and on Donna Janke’s Blog ‘Destinations, Detours & Dreams’.

Tyndall Stone is widely used throughout Canada, but as far as I know, has yet to make it to the UK … I looked at the following buildings during my recent trip to Vancouver and Banff National Park.

In Vancouver, the Tyndall Stone-clad Terminal City Club is on West Hasting’s street and the same building occupied by the Lion’s Pub fronting onto West Cordova Street.

In Banff National Park, the Fairmont Chateau Lake Louise has Tyndall Stone cladding on the ground floor and the Fairmont Banff Springs uses polished Tyndall Stone as paving, cladding and dressings in the impressive entrance hall.

My Sister, thrilled at finding the Receptaculitid Fisherites on the Terminal City Club in Vancouver. It is on the slab above the right side of the porch.

All photos used here are by Ruth Siddall and should be cited as such.

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To cite this article:

Siddall, R., 2017, Tyndall Stone: An Iconic Canadian Building Stone., Orpiment Blog, published 09/09/2017: http://wp.me/p53QQu-bC

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References and further reading

Finney, S. C. & Nitecki, M. H., 1979, Fisherites n. gen. reticulatus (Owen, 1844), a New Name for Receptaculites oweni Hall, 1861., Journal of Paleontology., 53 (3), 750-753.

Gingras, M. K., Pemberton, S. G., Muelenbachs, K. & Machel, H., 2004, Conceptual models for burrow-related, selective dolomitization with textural and isotopic evidence from the Tyndall Stone, Canada., Geobiology, 2, 21–30.

Janke, D., 2017, Winnipeg and Tyndall Stone: Fossils and Architecture., Destinations, Detours & Dreams.

Jin, J., Harper, D. A. T., Rasmussen, J. A. & Sheehan, P. M., 2012, Late Ordovician massive-bedded Thalassinoides ichnofacies along the palaeoequator of Laurentia., Palaeogeography, Palaeoclimatology, Palaeoecology 367–368 (2012) 73–88.

Kendall, A.C., 1977. Origin of dolomite mottling in Ordovician limestones from Saskatchewan and Manitoba. Bulletin of Canadian Petroleum Geology, v. 25, p. 480-504.

McCracken, A.D., Macey, E., Monro Gray, J.M. & Nowlan, G. S., 2007, Tyndall Stone., Natural Resources Canada.

Sheehan, P.M. and Schiefelbein, D.R.J., 1984. The trace fossil Thalassinoides from the Upper Ordovician of the eastern Great Basin: deep burrowing in the early Paleozoic. Journal of Paleontology, v. 58, p. 440-447.

Shields, C., 1993, The Stone Diaries., Fourth Estate., 361 pp.

Thorsteinson, J., 2013, Tyndall Stone., Winnipeg Architecture Foundation Inc., 13 pp.

Gillis Quarries

 

 

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Whales on the Road

This post is a departure from my usual blogs about rocks, minerals, pigments and err … stamps. It is about dead whales touring the country on the back of lorries. There are not many things these days that provide pretty much no hits when Googled, but this subject seems to be one of them. You may well be asking why I would be Googling ‘Whales’ ‘Lorry’ ‘Supermarket Car Park’. Here is the answer.

I was talking to my colleague Jack Ashby at the UCL Grant Museum of Zoology about their upcoming #WhaleWeekender extravaganza, wherein the skeleton of an 8 m long northern bottle-nosed whale will be assembled for the first time since the 1940s. You can read more about this in Jack’s blog here. The whale in question had toured the country before ending up, disarticulated in the Grant Museum. I told Jack that I remembered seeing a whale in the back of a truck when I was a kid in Salford in the early 1970s. Jack looked at me like I had said 1870s. On reflection there is certainly a circus side-show, freak-show element to this experience. Until speaking to Jack, I have not thought about this for years.

I went home and got onto Google, expecting to find photos, local newspaper articles etc., but nothing came up. However I did discover two illuminating pieces about the phenomenon that was whale tours, one in the Guardian and another from the BBC. Both remark that these events went largely unreported, although it seems that they were not uncommon between the 1950s and early 1970s. The touring whales were obtained from Norwegian whalers and were given imaginative names such as ‘Jonah’, ‘Hercules’ and ‘Goliath’, although one was called ‘Eric’.

This picture from the BBC & Pathé shows a whale on tour, probably in the 1960s, with body parts helpfully labelled. Note the instrument of death, a harpoon, at lower right. This was almost certainly taken in the north of England. Look at that roofline. Look at those kids.

The BBC article makes statements such as ‘In an era of limited television, staring at a dead whale was seen as a good pastime’ and ‘Parents took their toddlers to see the carcasses’. Yup. That was me.

I did find some memories via social media, from people of my generation living in my home town of Walkden in Greater Manchester. Many comments were along the lines of ‘Does anyone remember the whale in Walkden? Or am I imagining it?’ The following comments showed that some did remember, many didn’t, but no one had any photos. There seems to be very little evidence that this actually happened. However someone did mention they had seen a mammoth and had a picture to prove it … but that is another story.

For those of us born in the second half of the twentieth century, one is often conscious that one’s memories are influenced by images (so now I am beginning to remember that I may have seen the mammoth too …) but I can safely say that this is not the case with the Walkden whale. This is what I remember. I was very young at the time, probably between 5 and 7 years old, which would put this event at between 1972-1974. My dad had heard about this whale and said ‘shall we go and have a look at it?’ So off we went to Scan car park where the whale truck was pulled up. Scan was a hypermarket, the first one in our area and it was located just off Manchester Road in Walkden (it is now a branch of Tesco). I remember it was rainy and misty. It could have been Winter, it could have just been Salford. There were not many people there. I suppose my Dad paid someone.

And there it was in the back of a lorry with the sides let down. A whale, huge and black, maybe 10 or more metres long. It was a big truck. It didn’t look real, it looked like it was made of a hard, black plastic. I asked my Dad if it was real (whilst keeping tight hold of his hand) and he replied ‘Oh yes, of course it is’. I don’t have any memory of smell (but I think that’s just me, I don’t have any memories of smell at all). In retrospect I suspect it was coated with tar or something. I have no idea what species of whale it was. All I really remember was its eye. I just remember staring at its eye. I imagined whales to have big eyes but this was small and beady, surrounded by folds of flesh. I seem to remember the lorry was blue. We looked at it for around ten minutes and then left. I haven’t really thought of it since. My Dad was a very keen photographer and in retrospect I am astonished he did not bring his camera and take a photo. I don’t have any memories of a photo, but perhaps I should scour my Dad’s slides and negatives. You never know.

Sadly my Dad died ten years ago. I phoned my Mum, wondering if I could extract any further information, and this is how the conversation went

Me: Do you remember Dad and me going to see the whale?

Mum: In Wales?

Me: No, in Scan.

Mum: In Wales??

Me: No, in Walkden, a whale – not Wales

This went on for a while, alliteratively, but sadly Mum had neither recollection of my Dad and me going to see it, nor any memory of a photo recording the event (NB My Mum now lives in Wales). I am beginning to wonder if I imagined this too – were it not for the fact that it is the only non-skeletal whale that I had ever seen until the 1990s and I can see its dead eye in my mind now.

[NB: The whale I saw in the 1990s was a dead, beached whale on the island of Mull. I don’t remember how that smelled either, but it must have been shocking].

I would love to hear from anyone who does remember the Walkden whale, but I am also interested to hear from anyone else who remembers other whale tours, despite them being something that can be gladly consigned to history. #WhaleMemories

 

 

Barnicoat, B., 2015, The mystery of Jonah, the giant whale who toured the UK in the 1950s., The Guardian, Wednesday 8^th July.

Bell, B., 2016, When dead whales went on tour., BBC News Online, 1^st May. 

Photograph of a whale’s eye is from http://www.whalesforever.com/whale-senses-sight.html

 

Inside the Bartlett Brick

The new building at 22 Gordon Street houses The Bartlett School of Architecture. Completed in 2017 and designed by Hawkins\Brown Architects, the building has recently been named on the shortlist for The Architect’s Journal AJ100 Building of the Year prize and the RIBA London Awards. The structure is a retrofit of the former Wates House, the ghost of which still exists in the core of the building. What replaces it is a spacious, fit-for-purpose building for the UCL School of Architecture.

Now those of you that know me and know that my interests in the fabric of UCL are mainly biased towards the use of stone, may have assumed that I was disappointed to see a brick and concrete structure appear on the corner of Gordon Street and Endsleigh Gardens. Not so. I declare a fondness for both materials, though I confess to prefer my concrete to be around 2000 years old, the bricks used to clad 22 Gordon Street are rather special.

I am very grateful to the Bartlett’s Kevin Jones for supplying me with a specimen of ‘The Gordon Street Klinker’ a brick made specially for the construction of the building by the German brick makers Janinhoff.

Janinhoff make a great deal of bricks of different compositions, but mainly to a standard size. The Gordon Street Klinker is slimmer and longer than the standard bricks in their repertoire. 140,000 of these bricks, measuring 290 x 52 x 70 mm were used on the façade.

The brick is water-struck and twice fired. The water-struck brick making process works well for high moisture content, high plasticity clays. The clay is ‘struck’ in a wooden mould, and the large amount of water present allows for the mould to be easily removed, without the clay sticking to it. Evidence of this process can be seen in the puckered, ‘troweled’ surface of these bricks and the lip from clay overhanging the top of the mould. Lower water content clays need to be ‘sand-struck’; i.e. the mould is coated with sand which stops the brick from sticking to it.

Evidence that these bricks are hand made can be seen in this example from the Endsleigh Gardens façade of the Bartlett’s 22 Gordon Street Building …

Look closely and you can see the brick maker’s fingerprints …

Janinhoff fire their bricks in a circular, so-called Hoffman Kiln which can operate continuously. Patented by Friedrich Hoffmann in 1858, these are the standard brick kilns used worldwide today. They are large circular or oval structures often with a central chimney. The interior has firing chambers radiating out from the central space (below the chimney). The kilns are fired by a movable ‘fire wagon’ which can travel on rails around the interior, firing each chamber consecutively.

The Gordon Street Klinker is coal fired at maximum temperatures of 1200°C. Looking at the surfaces of the bricks, ‘firing ghosts’ are seen patterning the surface of the bricks. This tells us how they were stacked in the kiln, subtly changing the oxidation of the brick surfaces where they touch each other.

Above: Janinhoff’s Hoffmann kiln, showing bricks being stacked ready for firing and also note the use of spacers and other kiln furniture.

The grey colour of the bricks indicates a low-iron content clay. Such materials are available in the northern Germany and Denmark deposited as Quaternary glacial clays. The Jutland Peninsula lay at the southern edge of the ice sheet during the last glaciation and the clays were deposited as the ice sheet retreated between 20 – 10 thousand years ago.

To be workable, reduce shrinkage and cracking on drying and firing and be strong, brick clays need to contain inclusions or temper. Inclusions are natural mineral grains that occur naturally in the clay whereas a temper is added by the brick makers and can include both mineral and organic particles.

To look inside the Bartlett bricks it is necessary to produce a thin section, a slice 30 µm thick for observation using polarising light microscopy. This technique is routine in geology for examining rocks and identify their component minerals. As ‘synthetic stones’, ceramics may also be analysed in this way under the discipline of ceramic petrology.

Under the microscope, the Bartlett bricks have an almost isotropic (opaque) clay matrix indicating that the clay minerals have broken down and have begun to melt. This indicates that the brick has been fire in excess of 1000°C (and indeed we are aware from the manufacturers that temperatures of 1200°C were attained). It is not possible to distinguish whether or not the brick clay contained inclusions or it has been tempered, or perhaps both! Mineral particles present are dominantly quartz, but chert, feldspar and zircon are also present, indicating granitic rocks in their source. Grains are poorly sorted ranging from very fine (a few 10s of microns diameter) to particles of around 0.5 mm, the latter just visible to the naked eye. It is reasonable to expect that the finest portion are naturally occurring inclusions in these glacial clays.

The photomicrographs below show the brick photographed in plane polarised light and under crossed polars, x 40 magnification.

The mineral grains are sub-rounded to sub-angular, indicating a natural sand source (i.e. not mechanically crushed). The composition is clearly granitic as indicated by the feldspar, zircon (this in typically tiny grains) and the large quartz grains with fluid inclusion trails. Some of these features are seen in the photomicrographs below. Left, the large grain in the centre is a feldspar; x 40 magnification, the field of view is ~ 3.5 mm. Middle and Right, quartz grains with inclusion trails, x 100, the field of view is ~ 1.5 mm.

Citation

Siddall, R., 2017, Inside the Bartlett Brick, Blog: Orpiment https://orpiment.wordpress.com/2017/06/02/inside-the-bartlett-brick/

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