Xonotlite

Xonotlite
Combination piece with radial fibrous inesite and xonotlite
General
Category	Inosilicates
Formula (repeating unit)	Ca6Si6O17(OH)2
Strunz classification	9.DG.35
Dana classification	66.3.1.1
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P2/a
Unit cell	879.33
Identification
Color	White, grey, pale pink, lemon white, colorless
Cleavage	Perfect, Good
Fracture	Splintery, tough
Mohs scale hardness	6.5
Luster	Vitreous, silky, pearly
Streak	White
Diaphaneity	Transparent, translucent
Specific gravity	2.70 - 2.72
Density	Measured: 2.70 - 2.72 Calculated: 2.71
Optical properties	Biaxial (+)
Refractive index	nα = 1.583 nβ = 1.585 nγ = 1.595
Birefringence	0.012
2V angle	50°
Ultraviolet fluorescence	Short UV = weak gray-white Long UV = weak white
Common impurities	Fe, Mn, H2O

Xonotlite or eakleite is a mineral named by Karl Friedrich August Rammelsberg in 1866. The name originates from its discovery locality, , Puebla, Mexico. Although it was discovered in 1866, it was first described in 1959. It is approved by the IMA, but it is a grandfathered species, meaning the name supposedly represents a valid species til this day.^[1]

Properties[]

Xonotlite is an ino-silicate with double dreier chains, of which several polytypes are known. The known polytypes are Ma2bc, Ma2b2c and M2a2bc. It is a mineral related to the tobermorite group. It can be colorless, gray, light gray, lemon white, or pink. It is transparent with a vitreous to silky luster. It leaves a white streak. Xonotlite is rated 6.5 on the Mohs scale of hardness. It crystallizes in the monoclinic - prismatic crystal system,^[1] with typically an acicular crystal form or habit, meaning it occurs as needle-like crystals. It is massive, meaning individual crystals are hard to tell apart as they form large masses. It mainly consists of oxygen (42.52%), calcium (33.63%) and silicon (23.57%), and includes hydrogen (0.28%). It is a luminescent mineral, under short ultraviolet light it has a weak gray-white fluorescence, and under long UV it is weak white. It isn't a magnetic mineral, and is not radioactive.^[2]

Environment and mining[]

It occurs as veins in serpentinite and contact metamorphism aureoles.^[2] Associated minerals include apophyllite, diopside, stilbite, tobermorite, clinohedrite, thaumasite, laumontite and wollastonite.^[3] The most common impurities include iron, magnesium and hydrogen dioxide impurities. It ihas many type localities, the most honorable one being Tetela de Ocampo, Mexico.^[1]

Xonotlite from Italy.

References[]

Wikimedia Commons has media related to Xonotlite.

• Webmineral data
• Mineral Data Publishing
• Mindat with location data

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