"Caswellite" (pseudomorphs of Grossular after Hendricksite mica)

Item Description

Specimens of "Caswellite" are rare on the market, and even in most collections. The material was originally a valid mineral species dating back to 1894, but is now defined as a variety of Grossular which has formed pseudomorphs after Hendricksite mica. Typically one will see Vesuvianite associated with these specimens, and you can see it on this piece as well. The almost resinous / semi-metallic bronze colored "Caswellite" can be seen all over the piece. A great example of this hard to find material from this most classic of localities in New Jersey. The piece is accompanied by a label from the Franklin Mineral Museum.