If it’s very soft and feels a bit greasy and/or soapy, there’s a good chance it’s talc.
Physical Properties |
|
| Chemical formula | Mg3Si4O10(OH)2 |
| Class | Phyllosilicate Sheets of linked tetrahedra |
| Crystal system | Monoclinic |
| Habit | Usually massive Usually very fine-grained Rare tabular pseudohexagonal |
| Color | Gray White |
| Hardness | 1 |
| Specific gravity | 2.8 |
| Cleavage | Perfect basal (001) |
| Fracture | Flexible |
| Luster | Resinous Silky |
| Transparency | Translucent |
| Streak | White |
Optical Properties |
|
| PPL | Colorless Non-pleochroic |
| XPL | 1st order grays and yellows May appear smeared or poorly defined |
| δ | 0.05 |
Special properties |
Soft, greasy feel |
| after Perkins, 320 |
Talc in Hand Sample
Talc
A different talc
Talc in soapstone
Talc in Thin Section
Thin Section GigaPans
Talc, plane polars
Talc, crossed polars
Talc tremolite schist, plane polars
Talc tremolite schist, crossed polars
