Orthoclase pseudomorph after Leucite (rare matrix specimen)

Item Description

This is the ONLY matrix specimen of this material that we've ever seen. This small cabinet display specimen features an impressive well-preserved pseudomorph of soft beige colored Orthoclase which has replaced a textbook trapezohedral crystal of Leucite from this locality near the border with Bohemia. The pseudomorph measures 3.1 and is complete all around, totally undamaged, and sits beautifully centered on the matrix. I personally think that these are quite intriguing pseudomorph for a few reasons. A feldspar species (Orthoclase) is replacing a feldspathoid species (Leucite), which is interesting because feldspathoids are defined as rock forming minerals that are lacking the necessary silica to actually form feldspar. So in this case we have the lower silica bearing Leucite that was replaced by a higher silica bearing Orthoclase to create these wonderful pseudomorphs. The habit of the original leucite crystals is a trapezohedron, as the crystal system for the species is actually cubic at around 900°C. You can look up Leucite and see that it is listed as being tetragonal in habit because the actual crystal structure changes once the species cools below 700-600°C, so these crystals were HOT when they formed, and possibly were still in the process of growing when additional silica was introduced, turning them into Orthoclase in the final stages of their formation. A rare and desirable piece of this hard to find material. Valued $1,500.
From the collection of Kurt Hefendehl (#597 D), a well-known German collector all over Europe with worldwide contacts to dealers and collectors. He started collecting seriously at the age of 14 and his great and varied worldwide collection reached over 6000 pieces. He was very active mineralogically until shortly before his passing in 2020 at the age of 82. Considering his collection had a large number of pieces, it still had an unusually high standard of quality from most worldwide localities. He particularly specialized in all classics as well as minerals of the Black Forest, where he spent much time collecting. His Black Forest and German subcollections went to his good friend Wolfgang Wendel. We at The Arkenstone have the privilege of offering the remainder of this great worldwide collection for the foreseeable future through our various platforms.