PRECIOUS STONES.	219
	the variety of Garnet known as Hessonite, and with Mica. In chemical composition it is a calcium magne­sium metasilicate, usually with a variable amount of iron, that with the greater amount being darker in colour and of greater density. Diopside was originally found at the Mussa Alp, in the Ala valley in Piedmont, hence the names Alalite and Mussite. It is also
	found at the Schwarzenstein Alp, in the Tyrol, and at De Kalb, in New York State. When cut as a gem the clear green transparent forms are used, and they are either step or table cut. They are chiefly used in the countries where the mineral is found. It is rather difficult to distinguish from Olivine, but Diopside is the softer mineral of the two. The green Chrysoberyl and green Idocrase are both denser than Diopside, while Tourmaline and Epidote are more