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Mineralpedia Details for Tobermorite

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Tobermorite

Tobermorite

Tobermory, on the Island of Mull in Scotland, is the namesake and type locality for the mineral Tobermorite. It occurs as aproduct of hydrothermally altered calcium carbonate rich rocks, as well as a product of metamorphism. It will sometimes fill cavities in basaltic rocks.  Tobermorite is actually a group name that includes the 9-Å, 10-Å, 11-Å, and 14-Å hydrates. Tobermorite 11-Å is the group member actually called Tobermorite, whereas Tobermorite 9-Å is riversideite, Tobermorite 10-Å is oyelite, and Tobermorite 14-Å is plombierite. Occasionally, some Tobermorite 11-Å, Tobermorite, will shrink upon dehydration.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/tobermorite.pdf

Formula
Ca5Si6O16(OH)2┬ĚnH2
Crystal System
Orthorhombic 
Crystal Habit
Fibrous, Aggregates, Radial 
Cleavage
Perfect, Imperfect, None 
Luster
Silky 
Color
white, light pink white, reddish white 
Streak
white 
Class
Orthorhombic - Disphenoidal 
Hardness
2.5 
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Tobermorite from Crestmore, Riverside Co., California, United States

Tobermorite
            from Crestmore, Riverside Co., California, United States

PXRD confirmed this to be structural type 14A of the Tobermoreite group. An incredibly complex group of minerals. Like almost everything else at Crestmore, it is a pearly white, platy calc-silicate. These crystals occur in radial bunches to about 1mm.

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