Pharmacosiderite (ex Kay Robertson Collection)

Item Description

Tiny brilliant green cubic crystals of this potassium iron arsenate, and the namesake for its own group sit atop iron-stained Quartz matrix. Pharmacosiderite is found in the oxidized areas of ore bodies containing iron, as it forms as a secondary crystallization when the iron breaks down underground. The crystals on this piece are small, but they are brilliant and very fun to view under the microscope. Ex Kay Robertson Collection (#7233). The piece also has a blue number (7206) attached to it which according to the back of the label states it's from the Frenzel Collection (though the locality may not be correct). It certainly looks like another Pharmacosiderite I found online for reference. The piece was purchased from Ron Bentley in March of 1974. is Kay is a prominent California collector, who specialized in European classics (see the article in the March-April, 2007 Mineralogical Record and the 50+ page article in the German Magazine "Mineralien Velt" November-December 2017).