BetaHgS

BetaHgS is the beta polymorph of mercuric sulfide (HgS). It is commonly referred to as metacinnabar and represents the cubic form, in contrast to the red cinnabar form (alpha-HgS), which is hexagonal/trigonal.

In terms of structure, beta-HgS adopts a zinc blende–type cubic crystal arrangement, with Hg and S arranged in a tetrahedral coordination. It is typically black or dark gray in appearance and is less common than the red cinnabar form in natural samples.

Beta-HgS occurs mainly as a metastable phase in nature. It can be present as rare inclusions or intergrowths within cinnabar-bearing deposits. It can also be produced synthetically by rapid precipitation from solution or by transforming alpha-HgS under certain thermal conditions. Because it is metastable at ordinary conditions, beta-HgS can gradually convert to the more stable alpha-HgS over time or upon heating.

The form is of interest primarily to mineralogists and solid-state chemists. It provides insight into phase transitions and the behavior of mercury sulfide under varying temperature and pressure. Beta-HgS is not used commercially as a pigment or in large-scale applications; its relevance lies mainly in academic study and mineralogical characterization.

Safety and handling are important considerations due to the toxic nature of mercury compounds. Proper precautions are essential when working with HgS forms, including beta-HgS, to minimize exposure.

See also: cinnabar, metacinnabar, mercuric sulfide.