What is Natrochalcite?
Natrochalcite is a blue-green hydrated sodium copper sulfate from oxidised copper deposits and sulfate-rich cavities.
Mineralogy and crystal structure
Reference formula: NaCu2(SO4)2(OH)·H2O. Natrochalcite is a monoclinic hydrated copper sulfate and belongs to a family of related sodium and potassium copper sulfates. Its colour is attractive but the mineral is soft, soluble and chemically sensitive. Natrochalcite is classified with sulfates and has a monoclinic crystal system. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 3.4–3.6.
Colour, lustre and habit
Typical colours include blue, blue-green, green. The usual prismatic, fibrous, crusty habit and vitreous, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Natrochalcite forms in or is associated with oxidised copper ore veins, mine workings and sulfate-rich hydrothermal cavities. Important documented localities include Chile, Argentina, Peru, Germany, Australia and the United States.
Blue-green copper sulfate in a delicate crust
Natrochalcite makes secondary copper chemistry easy to see: a blue-green coating can carry sodium, sulfate and water in a structure that formed after the primary ore.
Collecting and care
Keep dry and enclosed; avoid water, acids, abrasion and dust from broken material.
