Palygorskite
Palygorskite or attapulgite is a magnesium aluminium phyllosilicate with the chemical formula (Mg,Al)2Si4O10(OH)·4(H2O) that occurs in a type of clay soil common to the Southeastern United States. It is one of the types of fuller's earth. Some smaller deposits of this mineral can be found in Mexico, where its use is tied to the manufacture of Maya blue in pre-Columbian times.
| Palygorskite | |
|---|---|
A sample of palygorskite | |
| General | |
| Category | Phyllosilicate |
| Formula (repeating unit) | (Mg,Al)2Si4O10(OH)·4(H2O) |
| IMA symbol | Plg |
| Strunz classification | 9.EE.20 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/m |
| Unit cell | a = 12.78 Å, b = 17.86 Å, c = 5.24 Å; β = 95.78°; Z = 4 |
| Identification | |
| Color | White, grayish, yellowish, gray-green |
| Crystal habit | Lath shaped crystals, fibrous and compact masses |
| Cleavage | Distinct/good, good on {110} |
| Tenacity | Tough |
| Mohs scale hardness | 2 – 2.5 |
| Luster | Waxy, earthy |
| Diaphaneity | Translucent |
| Specific gravity | 1 – 2.6 |
| Optical properties | Biaxial (−) |
| Refractive index | nα = 1.522 – 1.528 nβ = 1.530 – 1.546 nγ = 1.533 – 1.548 |
| Birefringence | δ = 0.011 – 0.020 |
| Pleochroism | X= pale yellow Y=Z= pale yellow-green |
| References | |
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.