Arsenic Family Minerals

Part II: Erythrite, Realgar, Orpiment and Scorodite Add Rich Color to a Collection

- Bob Jones

There’s a large number of minerals whose chemistry includes arsenic combined with oxygen: the arsenides. Many of them are very rare or come from some obscure locality that has not produced enough specimens to add significantly to the collector market. Fortunately, however, there are a significant number that are readily available in quantity to please all collectors. These include adamite, legrandite and mimetite, which have been described in the literature often enough for information on them to be readily available.

Historically, a lovely suite of arsenic species was commonly collected in Cornwall, England. Several of them were new species at the time, and enough specimens were found to supply the collector and scientific markets. Some of these specimens still survive today. The suite includes clinoclase, liroconite, chalcophyllite and olivenite, which were described in Part I of this series. A serious collector should keep an eye out for them, as they add a historical dimension to a collection. Even today, specimens of these arsenic species can be seen on display, and they may even show up for sale.

This leaves us with a suite of very colorful arsenides that is available in quantity today. The group includes such beauties as erythrite, realgar, orpiment, and very interesting, but uncommon, scorodite. The first three of these minerals are certainly common enough and are intensely colorful. Scorodite is not as common as the other three, but is found in several noted specimen localities, and this iron arsenate shows a curious color phenomenon.