Allactite
From Wikipedia, the free encyclopedia
| Allactite | |
|---|---|
 Picture width 3 mm |
|
| General | |
| Category | Arsenate mineral |
| Chemical formula | Mn7(AsO4)2(OH)8 |
| Crystal symmetry | Monoclinic, point group: 2/m, space group P21/a |
| Unit cell | a = 11.03 Å, b = 12.12 Å, c = 5.51 Å, β = 114°, Z = 2 |
| Identification | |
| Color | Brown, dark to light purplish red, brownish red, colorless to white |
| 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 | [1][2][3] |
Allactite is a rare arsenate mineral of metamorphosed manganese zinc ore deposits. It is found in Sweden and New Jersey, USA. Its name originated from Greek αλλάκτειν (allaktein) meaning "to change", referring to the strong pleochroism of the mineral.[2]
[edit] References
- ^ Allactite. Mindat
- ^ a b Allactite. Handbook of Mineralogy
- ^ Moore P. (1968). "Crystal chemistry of the basic manganese arsenate minerals: II. The crystal structure of allactite". American Mineralogist 53: 733–741. http://www.minsocam.org/ammin/AM53/AM53_733.pdf.
| This article about a specific oxide mineral is a stub. You can help Wikipedia by expanding it. |
