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 star-stones.
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: