BCGS

Birmingham Building Stones Trails

 

Trail 3: Around the Shops continued

 

4. 43 Temple Row
Originally built in 1980 for the Trustee Savings Bank by James A. Roberts Associates, this building is now occupied by Lloyds Bank. The most famous rapakivi granite, Baltic Brown, is used to clad this building and this continues along the façade on Cherry Street, providing excellent surfaces at eye-level to examine the textures and mineralogy of this rock. ‘Rapakivi’ is a Finnish word meaning ‘rotten rock’; a name coined due to the rubbly, surface weathering encountered in the Wiborg Batholith from whence this rock is quarried on the Finnish-Russian border. However the phrase ‘rapakivi granites’ applies to a range of anorogenic granites intruded between 1.6 and 1.5Ga in a zone extended from the Baltic Shield to the Southern USA. The variety we see here is the most well known and belongs to a group of rapakivi granites called wiborgites. These have the classic ‘ovoid’ textures of rounded, pink-brown potassic feldspars, rimmed by green plagioclase. Modern understanding of megacrysts in granitic melts is moving away from the interpretation that these are primary melt features and it is generally understood that these represent sub-solidus crystal growth.

 
Follow Cherry Street to Corporation Street and turn left in front of House of Fraser (formerly Rackham’s) department store. Do look at the beautiful slabs of Baltic Brown en route!

5. House of Fraser Department Store
Along Cherry Street, the block that is 43 Temple Row steadily merges into the House of Fraser Department store, facing onto Corporation Street. The shop is largely clad with a fine to medium-grained grey granite of unknown origin. It is composed of white, milky quartz and feldspar with abundant black biotite and minor muscovite. The feldspars are slightly altered and sometimes appear to be brown. Around the shop windows are strips of red Balmoral Granite, which like Baltic Brown described above, is another popular Finnish Stone, and again is part of the suite of rapakivi granites. These varieties, lacking the distinctive ovoids, are know as pyterlites. Balmoral is quarried from the Vehmaa Batholith, near Turku on the coast of SW Finland. Mineralogically it is composed of brick-red potassic feldspars, very dark, smoky quartz, plagioclase, biotite and hornblende. It has been marketed as ‘Balmoral’ since 1903, a time when Scottish-style baronial architecture was very popular in Scandinavia and Finland and also because the stone was marketed to the British Isles through the port of Aberdeen.

Turn left along Corporation Street and walk to The Square Peg pub on the corner of Bull Street.

6. The Square Peg Wetherspoons Public House
The ground floor façade of this enormous pub is clad with a spectacular pink granite. We continue the Finnish theme as this is another rapakivi granite from Porkkala on the southern coast of Finland and is therefore called Porkkala Granite. It is a wiborgite variety with ovoids of rose-pink potassic feldspar rimmed with white plagioclase. These are not as well defined as in Baltic Brown and this is partly because this stone has also been deformed, having been emplaced along a fault zone. Translucent, pale-grey quartz and biotite are also present. A Portuguese granite, Rosso Porriño has been used to patch this stone on the Bull Street façade; this is finer-grained, equigranular granite, also rose pink, composed of pink potassic feldspar, plagioclase, grey smoky quartz and biotite. Like the Cornish and Sardinian granites, it too was emplaced during the end-Carboniferous Variscan Orogeny.

Continue along Bull Street and enter the Minories. Once open, this shopping centre was glazed over and remodelled by Peter Hing & Jones Architects in 1993.

7. The Minories
Synthetic stones, including terrazzo flooring, are mainly used in the interior, but once again we see the wiborgite Porkkala Granite used to great effect, this time highly polished to clad the walls. This surface makes examination of textures much easier. The other stone used here is a strongly banded, migmatitic, black and red gneiss used as circular features at the bases of the lamps. Unfortunately the precise origin of this stone is unknown but it is very probably from Brazil. Such stripy gneisses are often marketed under the generic name ‘Juparana’ named after a lake in Espirito Santo State, Brazil close to some of the earliest quarries for this type of stone.

Walk straight through The Minories and turn left onto The Priory Queensway. After a few tens of metres, turn left at Colmore Circus Queensway onto a footpath down to the imposing, post-modern, office block building of The Wesleyan.

8. The Wesleyan and General Assurance Building

This immense office tower is also designed by Peter Hing & Jones and was completed in 1991. Foster (2007) describes it as a ‘poor quality’ attempt at post-modernism, and I am inclined to agree with him. However my agreement is short lived, as Foster goes on to say that the building is clad with synthetic stone. It most certainly is not! This building, very much of its time, exploited the then, new to the market, spectacular granitoids and gneisses of Brazil. Shilston (1994) identifies this stone as Rosa Tramonto, and indeed there is a polished sample of ‘Rosa Tramonto’ in the Dudley Museum (Cat. 017606) which is certainly very similar and it would be easy to draw conclusions here. However ‘Rosa Tramonto’ is not a standard stone name; it may well have been a ‘local’ name given by the stone contractors. I have not been able to further provenance this variety of ‘Juparana’ gneiss. Nevertheless, it is a beautiful stone, a coarse-grained granitic gneiss-migmatite, composed of potassic feldspar and biotite.

Walk 3 continues on the next page…

 

 

References can be found on the last page of the walk (3.5).