Richard Bell's Wild West Yorkshire nature diary, Tuesday, 23rd October, 2007, page 1 of 2
THE LAYERS in Tiger’s Eye (left) have a texture that looks like the fibres of asbestos and that’s what the mineral originally consisted of; quartz has replaced the original asbestos fibres, creating what’s termed a pseudomorph. The mineral crocidolite also occurs in Tiger’s Eye. Crocidolite has nothing to do with crocodiles – the name is derived from the Greek krokis lithos, ‘fibre stone’. Crocidolite is acid-proof and is used in insulation.
Here’s a more familiar form of quartz (right); these crystals formed in a cavity as mineral-rich fluid and gases flowed through the rock. Quartz has six-sided crystals and it is harder than steel.
Often veined and banded, the medium-sized crystals in Serpentine have the appearance of snake-skin. The Lizard Peninsula in Cornwall gets its name from this rock. The large red crystal is jasper.
I'm here at Cliffe Castle Museum, Keighley, with members of the West Yorkshire Geology Trust for a day of activities centred on the museum's impressive mineral collection. I'm drawing along with children using pencil on paper (with a little wax crayon) which makes a change from my usual pen and ink and watercolour. 'Lead' pencils are made from graphite set in a clay matrix. Graphite is a form of carbon with a melting point of 3,500 °C. It is a thermal and electrical conductor and is used in nuclear reactors.
There's also an opportunity to work in colour with artist in residence Jane Foale whose recent swirling colour experiments (left) have been inspired by the mineral collection. Some of the minerals on display are the source of colours in the paintbox. In Jane's work they interact in unpredictable ways, often strikingly like the patterns in minerals, for instance Derbyshire Blue John. She has exhibited some of her colour work, set in perspex and backlit. If they hadn't been labelled I would have guessed that these were wafer thin sections of minerals. Jane suspects that some of the interaction of the pigments she has been using takes place at a molecular level and she plans to take a look at some of the interesting areas with a microscope.
Like others, I find the patterns in her work - and in the minerals - resemble satellite photographs of the surface of planets, or of nebulae. Jane suggests that this is because similar principles are at work on the micro and macro scale.
A colour leaflet on her work is available free of charge from the museum.
Cliffe Castle Museum
West Yorkshire Geology Trust