According to Hobbs (1901): "...irregular block-like masses of so-called 'white horse.' The 'white horse' somewhat resembles the dolomite, but has soapy feel and contains 50 per cent or more of ferric oxide. It appears to be a mixture of iron carbonate and talc, and elsewhere in the Salisbury district it has been mined for the iron which it contains. At the surface it weathers to a brown color owing to the hydration of the iron oxide."
Quality for species:
Poor for species, only of interest for locality collectors. (#)