Empressite

Empressite is a mineral form of silver telluride, AgTe. It is a rare, grey, hexagonal crystal with which can form aggregates of bipyrimidal crystals. Twins do not form. Density 7600 kg.m-3.Recent crystallographic analysis has confirmed that empressite is a distinct mineral with orthorhombic crystal structure, different from the hexagonal Ag5-xTe3 with which empressite has been commonly confused in mineralogy literature. At the same time, empressite does not appear on the equilibrium Ag-Te phase diagram , and therefore it is only metastable at ambient conditions. Given infinite time, it would phase separate into pure Ag5Te3 and pure Te.
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General Information:
 Chemical Formula:
AgTe
 Composition:
(Molecular Weight = 235.47 gm)
Silver 45.81 % Ag
Tellurium 54.19 % Te
 Empirical Formula:
AgTe
 IMA Status:
Approved IMA 1964
 Locality:
Empress Josephine mine, Saguache County and Red Cloud mine, Bolder County, Colorado, USA.
 Name Origin:
Named for the locality.
Physical Properties:
 Cleavage:
None
 Color:
bronze or light bronze.
 Density:
7.5 - 7.6, Average = 7.55
 Diaphaniety:
Opaque
 Habits:
Compact - Occurs as a compact mass., ,
 Hardness:
3.5 - Copper Penny
 Luster:
Metallic
 Streak:
grayish black
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