laumontite
Sign in to saveright|thumb|250px|Laumontite crystals Laumontite is a mineral, one of the zeolite group. Its molecular formula is , a hydrated calcium-aluminium silicate. Potassium or sodium may substitute for the calcium but only in very small amounts.
Key facts
- Mineral.fracture
- Uneven
- Mineral.mohs
- 4
- Mineral.name
- Laumontite
- Mineral.category
- Tectosilicate minerals
- Mineral.group
- Zeolite group
- Mineral.image
- Laumontita.jpg
- Mineral.imagesize
- 260px
- Mineral.IMAsymbol
- Lmt
- Mineral.strunz
- 9.GB.10
- Mineral.system
- Monoclinic
- Mineral.class
- Prismatic (2/m) (same H-M symbol)
- Mineral.symmetry
- C2/m
- Mineral.color
- White, colorless, yellowish, brownish
- Mineral.cleavage
- Perfect, two directions
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right|thumb|250px|Laumontite crystals Laumontite is a mineral, one of the zeolite group. Its molecular formula is , a hydrated calcium-aluminium silicate. Potassium or sodium may substitute for the calcium but only in very small amounts.
It is monoclinic, space group C2/m. It forms prismatic crystals with a diamond-shaped cross-section and an angled termination. When pure, the color is colorless or white. Impurities may color it orange, brownish, gray, yellowish, pink, or reddish. It has perfect cleavage on [010] and [110] and its fracture is conchoidal. It is very brittle. The Mohs scale hardness is 3.5-4. It has a vitreous luster and a white streak. It is found in hydrothermal deposits left in calcareous rocks, often formed as a result of secondary mineralization. Host rock types include basalt, andesite, metamorphic rocks and granites. It forms at a temperature of about , and becomes unstable above about , and so its presence in sedimentary rocks indicates that these have experienced intermediate diagenesis.