Acid and Basic Phosphates – Olivenite and Lazulite Composition

Olivenite
An arsenate and hydroxide of copper, Cu₃AsO₈.Cu(OH)₂. Orthorhombic. Prismatic, often in acicular crystals. Also reniform, fibrous, granular. H. = 3. G. = 4.1-4.4. Fusible at 2-25. Adamantine to vitreous luster. Color olive-green to blackish green; also shades of brown and yellow to white. Traslucent to opaque. With sodium carbonate on charcoal gives a copper globule. When ignited in C. T. with splinter of charcoal gives arsenical mirror. A little water when heated in C. T. Found rarely in oxidized portions of copper veins.

Lazulite
A phosphate of magnesium and aluminum, Mg (Al.OH)₂(PO₄)₂, with varying amounts of ferrous iron, replacing the magnesium. Monoclinic, usually in steep pyramids. Also massive, granular, to compact. H. = 5-5.5. G. = 3.05-3.1. Vitreous luster. Azureblue color. Translucen opaque. Infusinble. B. B. Swells, loses its color and falls to pieces. Insoluble. A rare mineral.