What is Mariposite?
Mariposite is instantly recognisable when vivid green mica cuts through white quartz. Its collector appeal comes from the contrast and from the geological association with altered, sometimes gold-bearing veins in California and other districts.
Mineralogy and crystal structure
Reference formula: K(Al,Cr)3Si3O10(OH)2. Mariposite is a chromium-rich green mica material, commonly related to fuchsite or chromium-bearing muscovite rather than a standalone fixed species. The structure shown is a representative muscovite-family model and the label should retain the variety/material relationship. Mariposite is classified with silicates and has a monoclinic crystal system. Typical hardness is 2–3 on the Mohs scale and specific gravity is approximately 2.7–3.0.
Colour, lustre and habit
Typical colours include apple-green, grey-green, white, silver. The usual foliated, micaceous, massive habit and pearly, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Mariposite forms in or is associated with hydrothermal alteration zones in gold-bearing quartz veins and greenstone environments. Important documented localities include California, the United States, Canada, Australia and New Zealand.
Apple-green mica with a gold-country history
Mariposite is instantly recognisable when vivid green mica cuts through white quartz. Its collector appeal comes from the contrast and from the geological association with altered, sometimes gold-bearing veins in California and other districts.
Collecting and care
Soft and cleavable; avoid abrasion, waterlogging and dust from crushed material.
