This is a choice crystal cluster of Hyalophane, an uncommon, barium-rich variety of potassium Feldspar that while known from other places, comes at its best and in display quality ONLY from the Zagradski Potok Mine. The piece is dominated by several, stacked crystal twins with superb luster, complex habit and sublime, translucent, pale straw-yellow color. The vibrance of this specimen is accentuated by its glassy luster and gemmy to translucent character. The crystal measures nearly 6 cm in every direction and has razor-sharp edges and faces. This is one of the best I have seen from this locality in any size, and is a perfect small cabinet specimen; and it is much better in person, as gemmy crystals can be very hard to convey online. This is an outstanding small cabinet example from a famous locale that exemplifies the best of the species. Hyalophane was previously considered a unique mineral species (and you will see it as such on old labels and on our website in the past) but has been reclassified recently and is now considered to be a variety of microcline or orthoclase feldspar, which contains substantial barium content. A stunning piece, complete all around, from the Anne and Bill Cook collection. They obtained it (there is a lbel) in the 1970s-1980s from Julius and Miriam Zweibel, the legendary dealers from Woodmere, New York. The Zweibels had the best, the beautiful...for them to deal in rarities, showed what the thought of this treasure.