Mineral - Acanthite
Acanthite
Chemical Properties
Mineral Class
Sulfides and sulfosalts
Toxicity
none
Formula
Ag₂S
Unit Cell
a=4.23 b=6.93 c=7.86 β=100° Z=4
Physical Properties
Hardness
2 - 2.5
Streak
gray
Density
Very Heavy (>6)
Cleavage
Fracture
conchoidal
Tenacity
Optical Properties
Color
blackgray
Birefringence
Luster
Metallic
Transparency
opaque
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
P2 1 /m (11)
Habit
dendritic, acicular, Octahedron, spear-shaped, Tetrahedron
Formation
hydrothermal in Ag-bearing veins
Paragenesis
Twinning
Polysynthetic twins on ( 1 11), contact twins on ( 1 01)
Rarity
Common
Synonyms
Acanthite
Composition
Elements
Mass
Ag
86.40
Se
1.60
S
12.00
Mexico (Palache 1952)
Groups and Members
Acanthite-Group
Name and first discovery : Named after the Greek word "akantha" for "thorns," acanthite's characteristic pointed crystal shape was first discovered near Jáchymov in the Czech Republic and described in 1855 by the Polish mineralogist Gustav Adolf Kenngott (1818–1897).
Chemistry : Dimorphic to cubic argentite, after which acanthite forms pseudomorphs (pseudocubic octahedra).
Synonyms : Argyrite, Daleminzite, Henkelite, Silver Luster, Soft Ore
Varieties : Zinc Acanthite
Abbreviation : Aca
literature
Palache, C., Berman, H., & Frondel, C. (1952). Dana's system of mineralogy. Geologiska Föreningen i Stockholm Förhandlingar , 74 (2), 218-219.