Feldspar var. Sanidine

Rare old time GEM Sanidine crystal. Feldspar is a mineral not ususally known for fine collector gem crystals, but at this locality in Madagascar, amazing water clear crystals are sometimes found. This is a doubly-terminated crystal in excellent condition, crystallized all around with exceptionally sharp form for the locality. The crystal has a strong yellow coloration and is internally transparent. The faces alternate from smooth and glassy on the narrow sides to a dimpled surface texture on the larger faces. Both ends have good bevelled terminations. Ex. Heinrich Prager collection.