New Mills U3A

Twenty members of the two geology groups, led by Derek Brumhead, studied some of the great variety of ornamental building stones of central Manchester. The photographs were taken by Pat Stanway and, with the accompanying descriptions, are shown in the order of the walk.

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Ornamental Stones of Manchester U3A Geology Field Trip Sunday 25th July 2010	(click on images to enlarge)
	(click on images to enlarge)
Twenty members of the two geology groups, led by Derek Brumhead, studied some of the great variety of ornamental building stones of central Manchester. The photographs were taken by Pat Stanway and, with the accompanying descriptions, are shown in the order of the walk.
Cenotaph, St.Peter's Square. Portland Stone, a Jurassic limestone from Dorset. The fossil shell fragments are made prominent by the solution weathering of the stone.
	The Bridgewater Hall. New Red Sandstone (Permian age) from Scotland. The red colouration (iron staining) shows it was laid down in desert conditions. Note the bedding.
Outside The Bridgewater Hall. 'Touchstone' by Kan Yasouda. Carrara marble from northern Italy. Marble is a former limestone which has been altered by heat and pressure bringing about recrystallisation of the calcite. The pure white variety has been used in famous statues (eg Michelangelo's 'David' in Florence).
	Midland Hotel. Two kinds of granite. Below, is a granite (from Peterhead in Scotland) with the minerals evenly distributed. The red mineral is feldspar. Above, is a granite from Shap, showing large crystals of feldspar. This is called porphyritic texture.
Close-up of polished granite. The red mineral is feldspar, the black mineral is ferromagnesian, and the white/grey mineral is quartz. These are the three essential minerals which make up any granite.
	Midland Hotel, showing the workmanship involved in shaping the blocks of hard granite. Dates from the 1890's.
Chinese Restaurant, Mosley Street. Larvikite from southern Norway. Its trade name is 'Emerald Pearl'. It is a very popular ornamental stone on account of the shimmering of its feldspar crystals. Viewed from one direction they look bright, from the opposite direction they look dark.
	Alexandra, Mosley Street. This stone comes from the top layer of the Portland Stone in the Isle of Portland. It is highly fossiliferous. Note the turret shells and bivalves which have been loosened by solution and have fallen out of the rock when it was cut.
RBS Mosley Street. Rusticated sandstone made up of coarse grains of quartz.
	Rapakivi granite from Finland. On the RSA building in York Street. It is easily recognised on account of its large ovoid feldspar crystals. This rock is over 1,500 million years old. On account of its attractiveness it is a popular ornamental stone.
Close up of Rapakivi granite, showing an ovoid feldspar crystal with green rim.
	York Street. A stone known in the trade as 'Multicolour'. Geologically it is a gneiss, that is granite which has been subjected to high heat and pressure while still underground (ie. it is a metamorphic rock) drawing the minerals out into bands in a flow pattern. It comes from India.
King Street, the former Reform Club. Columns of Shap granite.
	Former NatWest Bank, King Street. This show Larvikite, 'Emerald Pearl', in its polished form and its flame-textured and ribbed form, a startling contrast.
Pall Mall Court, King Street. A slate rock known as 'Lakeland green'. It is an altered volcanic ash from the Lake District, over 400 million years old. You can see the coarse and fine layers of ash (this helps to tell which way up the rock is - how?).
	Ship Canal House, King Street. Rusticated granite.
Ship Canal House. Close up of rusticated granite. Check the three minerals.
	St. Anns Church was built in 1709. It was originally built from quarried stone from Collyhurst (purplish colour), but has since been repaired with a variety of stones. This wasn't obvious until the church was cleansed of its soot!
Junction of Deansgate and Jackson's Row. A fine display of Hall Dale Sandstone from Derbyshire. It is cross-bedded, showing the deposition of sandstone under water from different directions.
	Statue of Gladstone in Albert Square, pointing the way to Central Station. The red granite is from Aberdeen.
Albert Square. Close up of the workmanship in the granite of Gladstone's Statue.

GEOLOGY