Aurichalcite and Gay- Lussite Composition & Structure

Aurichalcite
A basic carbonate of zinc and copper, 2(Zn, Cu)CO₃.3(Zn,Cu)-(OH_)2. In acicular crystals, forming drusy incrustations. H. =2. G. = 3.6. Pearly luster. Color pale green to blue. Infusible. Soluble in hydrochloric acid with effervescence. Solution turns blue with ammonia in excess, Fused in R.F. on charcoal with sodium carbonate gives nonvolatile coating of zinc oxide (yellow when hot, white when cold). Water in C. T. A rare mineral found in the oxidized zones of copper veins.

Gay- Lussite
A hydrous carbonate of calcium and sodium, CaCO₃Na₂CO₃.5H₂O. Monoclinic. In rude crystals with uneven surfaces. Often wedge-shaped Prismatic cleavage. H.= 2-3. G. = 1.99. Vitreous luster. Colorless, white , gray. Fusible at 1.5 giving yellow flame of sodium. Gives alkaline reaction after ignition. Effervesces in acids. Concentrated hydrochloric acid solution gives precipitate of calcium sulphate with sulfuric acid. A rare species, found in salt-lake deposits at Lagunillas, Venezuela and near Ragtown, Nevada.

Other rarer species in this division include hydrozincite, ZnCO₃aZn)OH)₂; trona, NaCO₃HNaCO₃2H₂O; hydromagnesite, 3 MgCO₃ Mg(OH)₂.3H₂O