About the Properties of Spodumenes, Dichroites, and Idocrase

SPODUMENE.

Spodumene is sometimes cut and polished as a gem, but its peculiar cleavage makes it a bad stone for the lapidary to cut and the jeweler to mount.

Its hardness is 6.5 to 7, specific gravity 3.13 to 3.19, and lustre, vitreous to pearly.

Grayish - green, greenish - white, and sometimes yellow or faint red are the colors. Its composition is:

Silica 64.2

Alumina 29.4

Lithia 6.4

Acids do not attack spodumene, and under the blow-pipe it fuses to a white glass.

This mineral is found in Sweden, the Tyrol, Ireland, Scotland, and the United States.

DICHROITE.

Dichroite is sometimes known under the mineralogical names of cordierite and iolite, and commercially as saphir d'eau, or water sapphire. This stone is remarkable for pleichroism, sometimes showing three different colors in as many directions, and when properly cut has often the star formation of the corundum starstones.

Water sapphire, as the blue specimens are called, is 7 to 7.5 in hardness, specific gravity 2.56 to 2.67, transparent to translucent, and frequently full of flaws. It is partially decomposed by acids, melts with difficulty before the blow-pipe, is vitreous to greasy in lustre, and is composed of:

Silica 49.

Alumina 32.

Ferrous oxide 7.

Magnesia 9.

Besides the saphir d'eau, which is blue, dichroite occurs colorless, bluish-white, yellowish-white, yellowish-gray to yellowish-brown, indigo to blackish-blue, and violet. This mineral is found in Ceylon, Spain, Norway, Sweden, Tuscany, Greenland, and Bavaria. Sapphire is harder and much heavier than dichroite.

IDOCRASE.

Idocrase or vesuvianite was first found amongst the ancient ejections of Vesuvius, and it is still found at Vesuvius in hairbrown to olive-green colors.

Vesuvianite is 6.5 in hardness, 3.35 to 3.45 in specific gravity, transparent to opaque, lustre vitreous to greasy. It possesses strong double refraction, is attacked by acids, and melts readily under the blow-pipe. Vesuvianite consists of:

Silica 37.75

Alumina 17.23

Sesquioxide of iron 4.43

Magnesia 3.79

Lime 37.35

In colors, this mineral shades from brown to black, yellow, pale-blue, and green, and it is found at Vesuvius, Alps, Piedmont, Mt. Somma, Etna, Norway, Sweden, Spain, Hungary, Urals, and the United States.

Transparent or strongly translucent specimens, in handsome green or brown varieties, are used for jewelry, principally, however, in Turin and Naples.