Fluorspars (Spato fluore)
This fossil also known under the names of vitreous spar and fossil spar, is only a fluorate of lime. It often accompanies metallic ores. Hill 83 observed that [p133] lead gives it a yellow colour and cubical form; iron renders it red and rhomboidal or octahedral; tin renders it black and violet or amethyst colour, and of a quadrilateral shape; manganese gives it a purple or delicate violet colour; copper renders it dark blue or greenish. When spar is heated by fire it becomes crackled. It takes a superb polish, but is difficult to work because it is so friable. The most beautiful specimens are found in Darbishire in England.
538. (133.1) Spato di Siena. White ground with long crystals and sardonyx coloured veins. (Rare).
539. (133.2) Spato di Darbishire. Yellow ground with sulphate of baryte and a great deal of lead, found at Chrich. (Very rare).
540. (133.3) Another from the same place. Ground of light amethyst colour, with some darker veins. (Rare).
542. (134.5) Another from the same place a mixture of transparent yellow, and white, found at Chrich. (Very rare).
543. (134.6) Another from the same place, called bleu Giovanni. It is of a deep purplish colour and found uniquely at Castelton. (Very rare).