Loading AI tools
From Wikipedia, the free encyclopedia
Allactite is a rare arsenate mineral of metamorphosed manganese zinc ore deposits. It is found in Sweden and New Jersey, US. Its name originated from Greek αλλάκτειν (allaktein) meaning "to change", referring to the strong pleochroism of the mineral.[3]
Allactite | |
---|---|
General | |
Category | Arsenate mineral |
Formula (repeating unit) | Mn7(AsO4)2(OH)8 |
IMA symbol | Ala[1] |
Strunz classification | 8.BE.30 |
Dana classification | 41.2.1.1 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/a |
Unit cell | a = 11.03, b = 12.12 c = 5.51 [Å], β = 114°, Z = 2 |
Identification | |
Color | Brown, dark to light purplish red, brownish red, colorless to white |
Crystal habit | Elongated prisms, bladed, tabular, rosette-like aggregates |
Cleavage | Distinct, {001} |
Fracture | Uneven |
Tenacity | Brittle |
Mohs scale hardness | 4.5 |
Luster | Vitreous, slightly greasy on fracture surfaces |
Streak | Gray to faint brown |
Specific gravity | 3.83 (meas.), 3.94 (calc.) |
Optical properties | Biaxial (−) |
Refractive index | nα = 1.755–1.761 nβ = 1.772–1.786 nγ = 1.774–1.787 |
Pleochroism | X = blood-red; Y = pale yellow; Z = sea-green |
2V angle | ~0° |
References | [2][3][4] |
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.