Hessite is a mineral form of disilver telluride (Ag2Te). It is a mineral consisting of a lead-gray sectile silver telluride often auriferous and usually massive. It is a mineral form of disilver telluride. It is a soft, dark grey telluride mineral which forms monoclinic crystals. Crystals are usually distorted or irregular, pseudocubic and modified, sectile, opaque grey to dark grey, sometimes shiny silvery. It is named after Germain Henri Hess (1802–1850).
General Information
- Category: Sulfide minerals
- Formula: Ag2Te
- Crystal system: Monoclinic
- Crystal class: Prismatic (2/m) (same H-M symbol)
Fig: Hessite
Properties
Hessite is generally gray in color and forms pseudo-cubic crystals despite being monoclinic. Its ability to be cut by a knife or its sectility is diagnostic as well as its associations. Stützite (Ag7Te4) and empressite (AgTe) are related silver telluride minerals.
- Color: Lead-grey, steel-grey
- Cleavage: Indistinct on {100}
- Tenacity: Sectile
- Mohs scale hardness: 2 – 3
- Luster: Metallic
- Streak: black
- Diaphaneity: Opaque
- Specific gravity: 8.24 – 8.45
- Optical properties: Anisotropic
Occurrence: In hydrothermal medium- and low-temperature veins; also in small quantities in some massive pyrite deposits. It occurs within low to medium temperature vein deposits.
Hessite is found in the US in Eagle County, Colorado and in Calaveras County, California and in many other locations.
Association: Calaverite, sylvanite, altaite, petzite, empressite, rickardite, gold, tellurium, pyrite, galena, tetrahedrite, chalcopyrite.
