Augelite



Augelite-crystal


Crystal system Monoclinic
Transparency Transparent
Luster Vitreous
Fracture Conchoidal
Cleavage 2, Perfect;
1, good prismatic;
1, pinacoidal
Specific Gravity 2.70
Hardness 5
Optical Character Biaxial + ; Double Refractive
Refractive index 1.574-1.588
Birefringence 0.14
Dispersion
Fluorescence None under ultraviolet
Pleochroism
Chemical Formula Al2PO4(OH)3
Comments Dissolves very slowly in hot concentrated HCL
Streak White

Augelite (AW-jell-ite) is an aluminum phosphate hydroxide with the formula Al2PO4(OH)3 that sometimes occurs in colorless or nearly colorless as well as slightly brownish crystals. The name is derived from the Greek auge, meaning "brightness", in allusion to the usual transparent, colorless crystals.

The finest augelite crystals transparent, colorless and up to one inch in diameter come from the Champion sillimanite mine in Mono County, California. It also occurs in small, sharp crystals forming druses in tin veins at Machacamarca, Potosi, and Ouro, Bolivia.

Augelite's cleavage and optic character will separate it from beryl. Its birefringence will separate it from labradorite.
Augelite's perfect cleavage is fairly easy to start, but although it is brittle, it is not sensitive to ordinary dopping temperatures. It should be polished with Linde A on wax. Crown angles of 42° and pavilion angles of 43° are effective.