Vote for your favorite mineral in #MinCup26! - Sphalerite vs. Anorthite Both zinc ore Sphalerite and calcium plagioclase feldspar Anorthite have perfect cleavage that will split cleanly if you hit them with a hammer, but only one can claim a larger split of your votes!
Besides being a major component of the pegmatite matrix in general, where it is massive, it is abundant in miarolitic cavities as euhedral crystals. Some show phantoms or inclusions of schernikite fibers and elbaite and some are encrusted with cookeite blebs or show surface pit scars where cookeite was naturally removed. One 1.8-meter pocket contained nothing but jet-black smoky quartz crystals up to 14 cm in length. Etched crystals or oddly-shaped overgrowths on earlier fragments of quartz also known. Beautiful, doubly terminated crystals are often penetrated by elbaite. "One of these crystals, very flat and with several tourmalines inclosed, was worn as a watch-charm by the son of M. P. Gillette. This crystal in its natural state has as fine a polish as though it had just come from the lapidary's hand." (Davis, 1901).
Habit:
hexagonal prisms with rhombohedral terminations, sometimes flattened or etched, or oddly shaped overgrowths on earlier fragments
Colour:
pale gray to black, brown
Quality for species:
Excellent - world class for species or very significant. (!!)
Gillette Quarry, Haddam Neck, Haddam, Middlesex County, Connecticut, USA