Globular, white tacharanite (diameter 2.5 mm) from Palagonia, Italy
General
Category
Mineral
Formula (repeating unit)
Ca12Al2Si18O33(OH)36
IMA symbol
Tch[1]
Strunz classification
9.HA.75
Dana classification
72.3.2.6
Crystal system
Monoclinic
Space group
A-centered
Unit cell
a = 17.07 Å, b = 3.65 Å, c = 27.9 Å β = 114.1° Z = 1 V = 1,586.80 Å3
Identification
Formula mass
2,180.68 g/mol[2]
Color
Milky white
Crystal habit
Cryptocrystalline
Cleavage
Perfect {001}
Fracture
Conchoidal
Tenacity
Tough
Mohs scale hardness
5
Luster
Vitreous, earthy, dull
Streak
White
Diaphaneity
Translucent
Specific gravity
2.33 – 2.36
Density
2.33 – 2.36 g/cm3 Calculated: 2.28 g/cm3
Optical properties
Biaxial
Refractive index
nα = 1.518 – 1.525 nγ = 1.530 – 1.537
Birefringence
0.0120
Dispersion
Relatively strong
Fusibility
Decompose
Common impurities
Fe, Mg, Na, K
Other characteristics
Non radioactive
References
[2][3][4]
Tacharanite is a calcium aluminium silicate hydrate (C-A-S-H) mineral of general chemical formula Ca12Al2Si18O33(OH)36 with some resemblance to the calcium silicate hydrate (C-S-H) mineral tobermorite. It is often found in mineral assemblage with zeolites and other hydrated calcium silicates.
C-S-H and C-A-S-H mineral phases are important hydration products of cements but can also be found, although much less frequently, in natural conditions in particular geological environments. The natural specimens are rare and of small size (often available only in limited quantity) but often well crystallised while the hydrated cement phases are disordered and cryptocrystalline or amorphous with a poorly defined stoichiometry denoted by the use of dashes in the abbreviations C-S-H and C-A-S-H.
^Warr, Laurence N. (18 May 2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. eISSN 1471-8022. ISSN 0026-461X. S2CID 235729616.
^ abBarthelmy, Dave. "Tacharanite Mineral Data". webmineral.com. Retrieved 27 December 2022.
^Mindat. "Tacharanite". mindat.org. Retrieved 27 December 2022.
^Handbook of Mineralogy (2001). "Tacharanite" (PDF). handbookofmineralogy.org. Retrieved 27 December 2022.
Tacharanite is a calcium aluminium silicate hydrate (C-A-S-H) mineral of general chemical formula Ca12Al2Si18O33(OH)36 with some resemblance to the calcium...
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