Alphacinnabar

Alphacinnabar is a crystal structure of cinnabar, which is the mineral form of mercury(II) sulfide (HgS). Cinnabar is known for its vibrant red color and was historically used as a pigment. While cinnabar typically crystallizes in the trigonal system (alpha-HgS), it can also exist in a cubic form, known as metacinnabar or beta-HgS. Therefore, alphacinnabar specifically refers to the trigonal polymorph of mercury(II) sulfide.

This crystalline structure is characterized by its rhombohedral lattice. Alphacinnabar is the thermodynamically stable phase of HgS at standard temperatures and pressures. Its formation is often associated with hydrothermal environments. The distinct crystal habit and optical properties of alphacinnabar contribute to its value as a mineral specimen and its historical significance in art and alchemy, though its toxicity due to mercury content necessitates careful handling.