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Cyanite

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54
GEMS.
The carbon of which we speak can be cut into facets on the mill like the diamond, and, in that case, it reflects light while still remaining perfectly opaque.
It is found in great abundance, and therefore can be had for from six to seven lire the carat.
Its dust is preferable to that of the diamond, on account of its low price, and is found exceedingly successful in engravings on pietra dura and in cutting cameos.
We must not mistake this substance for the ada­mantine spar of China.
XXI.
CYANITE.
The name of this stone comes from the Greek κυανό«, blue, which was given it on account of its colour. It has been known in various ages, and there is a tra­dition that it was wrought in England, under the reign of James I., by one Cornellius, a German artist, who called it seppara, which name it still retains in France.
The tint of the cyanite is Prussian blue, and occa­sionally it fades from that to grey or green.
It does not melt under the blow-pipe. It is trans­parent, and presents prismatic reflections, especially when cut smooth. Its specific weight is 3.5. It is not very hard, but scratches glass with its angles.
Carbon Page of 243 Cymophane
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