Diaspore
Diaspore is an aluminum oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but usually, as lamellar or scaly masses, the flattened surface being a direction of perfect cleavage on which the luster is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent.[3] It may be readily distinguished from other colorless transparent minerals with a perfect cleavage and pearly luster—like mica, talc, brucite, and gypsum— by its greater hardness of 6.5 – 7. The specific gravity is 3.4. When heated before the blowpipe it decrepitates violently, breaking up into white pearly scalesDiaspore is definitely a gem that is uncommon treasure quality crystals coming mainly from bauxite deposits at Marmaris, Yatagan, Mugla Province, Turkey. It is hard enough to be used in precious jewelry but too brittle. Some gems have actually very pleochroism that is strong colors changing from pale golden-green to mauve-brown. Very rarely, gems may display colors of dark and violet-blue red.
| Crystallography: | Orthorhombic – Dipyramidal |
| Crystal Habit: | As crystals, platy and elongated to acicular, to 40 cm; stalactitic, foliated, scaly; disseminated, massive. Twinning: to form heart-shaped twins or pseudohexagonal aggregates. |
| Cleavage: | [010] Perfect, [110] distinct, [100] in traces |
| Fracture: | Conchoidal |
| Tenacity: | Very Brittle |
| Moh’s Hardness: | 6.5 – 7.0 |
| Density: | 3.20 – 3.50 (g/cm3) |
| Radioactivity: | Not Radioactive |
| Color: | White, pale gray, colorless, greenish gray, brown, pale yellow, pink, lilac; color may vary with viewing direction in the same specimen, may show a color change from brownish green in daylight to raspberry pink in artificial light. |
| Transparency: | Transparent to Translucent |
| Luster: | Adamantine, Vitreous, Pearly on cleavage faces. |
| Refractive Index: | 1.700 – 1.752 Biaxial ( + ) |
| Birefringence: | 0.047 – 0.050 |
| Dispersion: | Weak |
| Pleochroism: | Strong; may be reddish brown to reddish violet; grayish green to green. |
