Jahnsite Subgroup (very rare)

Item Description

Here we have a wonderful example of what used to be called Jahnsite, but is now defined as the Jahnsite Subgroup, which included 13 different species of Jahnsite(!). Now I'm inclined to believe that this piece is likely Jahnsite-(CaMnMg), as is often the case with these pieces, and that would mean it's from the type locality, the famed Tip Top Mine in South Dakota. The species was named after Dr. Richard Jahns, a mineralogist who worked at Stanford University, and specialized in pegmatite environments and their minerals. Without question, the finest quality and most well-known examples of this very rare phosphate are those from the Tip Top Mine, and this piece is a great example featuring hundreds of micro crystals of a dark golden-brown to greenish-brown hue with brilliant sparkling luster, which are associated with a couple of partial radial "sprays" of Rockbridgeite on matrix. I should point out that there are transitions within a single crystal of "Jahnsite" from one species to another, and it's possible that Jahnsite-(NaFeMg) is also present on this specimen. The piece is best viewed with magnification, and once you get up close, you can see how beautiful the little crystals are. A really attractive and notably hard to find piece that dates back several decades.
From the worldwide mineral collection of Albert Lewis Kidwell (January 1, 1919 - August 16, 2008). Al was a well-known mineral collector and research geologist with Carter Oil Company and later Exxon Oil Company in Houston, Texas. The phosphate species Kidwellite was named in his honor in 1974.