Mineral Factbook

Talc

Mg3Si4O10(OH)2IMA symbol: Tlcgrandfathered

Talc is a silicate mineral with the formula Mg3Si4O10(OH)2, crystallizing in the hexagonal system. It has a Mohs hardness of 1-1.5, typically white, black, brown or gray in color, with a pearly luster, a specific gravity of 2.7-2.8. Its streak is white or green.

Photos

Talc specimen photo
Mai Seppel · CC BY-SA 4.0 · Commons
Talc specimen photo
Didier Descouens · CC BY-SA 4.0 · Commons
Talc specimen photo
Mai Seppel · CC BY-SA 4.0 · Commons
Talc specimen photo
Unknown authorUnknown author · Public domain · Commons

Crystallography

Crystal systemhexagonal crystal systemWikidata (CC0)
Space groupC 1 2/c 1
Cell (Å, °)a = 5.26, b = 9.1, c = 18.81; α = 90, β = 100, γ = 90
Cell volume886.681 ų, Z = 4
Axial ratios0.5780:1:2.0670calculated from COD 9008040
Source structureCOD 9008040 (Zeitschrift fur Kristallographie, 1934) — 1 of 3 structures

Physical properties

Density (calculated)2.826 g/cm³calculated from COD 9008040
Hardness (Mohs)
1single sourceWikidata (CC0)
1-1.5single sourceDana, System of Mineralogy, 6th ed. (1892)
Specific gravity
2.7-2.8 g/cm3corroboratedDana, System of Mineralogy, 6th ed. (1892)
Color
black, brown, gray, green, red, whitesingle sourceDana, System of Mineralogy, 6th ed. (1892)
Streak
whitesingle sourceWikidata (CC0)
green, whitesingle sourceDana, System of Mineralogy, 6th ed. (1892)
Luster
pearlysingle sourceDana, System of Mineralogy, 6th ed. (1892)

Chemistry (calculated)

Molecular weight379.27 g/molcalculated from the IMA formula
Composition (wt%)Mg 19.23%, Si 29.62%, O 50.62%, H 0.53%

Classification

Nickel-Strunz (10th)9.EC.05Wikidata (CC0)
Nickel-Strunz (9th)9.EC.05Wikidata (CC0)
Dana (8th)71.2.1.3Wikidata (CC0)