Crystopedia
IMA mineral species

Thaumasite

Ca₃Si(OH)₆(SO₄)(CO₃)·12H₂O

Unusual calcium silicate mineral with carbonate, sulfate and hexacoordinated hydroxysilicate anions. Responsible of a harmful concrete sulfate attack.

YellowWhite & Clear

Thaumasite specimen
Thaumasite-d06-80a.jpg · Wikimedia Commons (see file page for author & license)

Properties

⛏ Mohs hardness3.5
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💅🪙🍶🔪💎

A copper coin scratches it.

🔷 Hexagonal✏️ streak white
Chemical formulaCa₃Si(OH)₆(SO₄)(CO₃)·12H₂O
ElementsCa, Si, O, H, S, C
Crystal systemHexagonal
Mohs hardness3.5
Density—
Streakwhite
Color—
IMA symbolTma
Nickel–Strunz class7.DG.15

“—” means no reliable value in Wikidata yet. Check Mindat for full data.

🌍 Where it's found

Type locality (where it was first described): Åreskutan, Sweden · Åreskutan, Sweden

  • Type locality
  • Notable source / deposit
  • Country of origin

Marker positions are approximate (region or locality level). Type localities from Wikidata; notable sources curated by Crystopedia.

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