Gypsum vs Talc
| Property | Gypsum | Talc |
|---|---|---|
| Formel | CaSO4 · 2H2O | Mg3Si4O10(OH)2 |
| Kristallsystem | Monoclinic | Monoclinic |
| Mineralklasse | 07 Sulfates, Chromates, Molybdates, and Tungstates | 09 Silicates |
| Mohshärte | 1.5-2.0 | 1.0 |
| Farbe | Colorless, white, gray, yellow, brown | White, gray, green, pale blue |
| Glanz | Vitreous | Pearly |
| Strichfarbe | White | White |
| Transparenz | Transparent | Translucent |
| Spaltbarkeit | Perfect {010} | Perfect {001} |
| Bruch | Conchoidal | Uneven |
Key Differences
- ◆ Talc (hardness 1) is the softest mineral; gypsum (hardness 1.5–2) is slightly harder.
- ◆ Talc has a distinctive soapy feel; gypsum does not.
- ◆ Talc is a magnesium silicate Mg3Si4O10(OH)2; gypsum is a hydrated calcium sulfate CaSO4·2H2O.
- ◆ Gypsum is used extensively in plaster and drywall; talc is used in cosmetics and ceramics.
- ◆ Talc has pearly luster; gypsum can be vitreous, silky (satin spar), or massive (alabaster).