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
Talc, Plane Polars
Talc in plane polarized light.Magnification: 100xClick here to watch this grain rotate in XPL:https://viewer.gigamacro.com/view/i9AFlqUzKxbbK0i4Click here to…
Talc, Crossed Polars
Talc in cross polarized light.Magnification: 100xTalc in plane polarized light.Magnification: 100xClick here to watch this grain rotate in XPL:https://viewer…
Tremolite, Plane Polars
Tremolite in plane polarized light.Magnification: 40xRock: Talc-tremolite schistClick here to watch this grain rotate in XPL:https://youtu.be/jkghynKS-hQClic…
Tremolite, Crossed Polars
Tremolite in plane polarized light.Magnification: 40xRock: Talc-tremolite schistClick here to watch this grain rotate in PPL:https://youtu.be/w782ovG0SbAClic…