Pimelite
Pimelite was discredited as a mineral species by the International Mineralogical Association (IMA) in 2006, in an article which suggests that "pimelite" specimens are probably willemseite (which is approved), or kerolite (which is also discredited). This was a mass discreditation, and not based on any re-examination of the type material (assuming any exists). Nevertheless, a considerable number of papers have been written, verifying that pimelite is a nickel-dominant smectite. It is always possible to redefine a mineral wrongly discredited.
| Pimelite | |
|---|---|
| General | |
| Category | Phyllosilicates |
| Formula (repeating unit) | Ni3Si4O10(OH)2·4H2O |
| Strunz classification | 8/H.09-65 (8 ed) |
| Dana classification | 71.3.1b.5 |
| Crystal system | Hexagonal Unknown space group |
| Identification | |
| Formula mass | 554.5 g/mol |
| Color | Bright green, apple green, yellow-green |
| Crystal habit | Fine-grained, also fibrous |
| Cleavage | None |
| Fracture | Uneven to conchoidal |
| Mohs scale hardness | 2.0–2.5 |
| Luster | Waxy |
| Streak | White |
| Diaphaneity | Translucent |
| Specific gravity | 2.23–2.98 |
| Optical properties | Biaxial (−) Can appear isotropic due to fine grain size |
| Refractive index | Nx = 1.592 Ny = 1.615 |
| Pleochroism | Pale green, colourless to light yellow green |
| Solubility | Decomposed by acids |
| Other characteristics | Neither radioactive nor fluorescent Expands to 17.35 A using glycol Nonmagnetic |
| References | |
The mineral was erroneously assumed to be a nickel-rich talc in a paper published in the American Mineralogist in 1979, but it had already been determined to be a smectite as early as 1938, and this was confirmed in another article in the American Mineralogist in 1966. Both nickel-bearing talc and nickel dominant smectite occur at the type locality, Szklary, Ząbkowice Śląskie County, Lower Silesia, Poland.