nAtacamite(Min) An oxychloride of copper, usually in emerald-green prismatic crystals.
Century Dictionary and Cyclopedia
natacamiteA mineral consisting of the hydrated oxychlorid of copper. It exists abundantly in some parts of South America, as Atacama, in Australia, near Ambriz on the west coast of Africa, and in Arizona in the western United States. It occurs massive, or in small prismatic crystals of a bright emerald-green or blackish-green color. A granular form from Chili is called arsenillo. It also appears on copper long exposed to the air or sea-water.
Webster's Revised Unabridged Dictionary
From the desert of Atacama, where found
The oxychloride Cu4O3Cl2, 4H2O occurs in nature as the mineral atacamite.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 3" by Various