Aerinite

Aerinite (Ca₄(Al,Fe,Mg)₁₀Si₁₂O₃₅(OH)₁₂CO₃·12H₂O) is a bluish-purple inosilicate mineral. It crystallizes in the monoclinic system and occurs as fibrous or compact masses and coatings. It has a dark, vitreous luster, a specific gravity of 2.48 and a Mohs hardness of 3.

Aerinite
Aerinite from Spain
General
Category	Inosilicates
Formula	Ca4(Al,Fe,Mg)10Si12O35(OH)12CO3·12H2O
IMA symbol	Aer[1]
Strunz classification	9.DB.45
Crystal system	Trigonal
Space group	P3c1
Unit cell	a = 14.690(15), b = 16.872(15) c = 5.170(15) [Å]; β = 94.75°; Z = 1[2]
Identification
Color	Blue to blue-green
Crystal habit	fibrous
Mohs scale hardness	3
Luster	vitreous
Streak	bluish white
Diaphaneity	translucent
Specific gravity	2.48
Optical properties	Biaxial (−)
Refractive index	nα1.510(5), nβ = 1.560(5), nγ = 1.580
Pleochroism	Intense; X = bright blue; Y = Z = pale beige
2V angle	63° (calc.)
Dispersion	δ = 0.07
References	[3][4][2][5]

It is a low-temperature hydrothermal phase occurring in zeolite facies alteration of dolerites. Associated minerals include prehnite, scolecite and mesolite.^[3]

Its name comes from a Greek root "aerinos," meaning "atmosphere" or "sky blue".^[2] It was first described by Lasaulx (1876) from a specimen in the Wrocław museum that was obtained in Aragon, Spain.^[6] In 1882, the geologist Luis Mariano Vidal found the mineral in situ in Caserras del Castillo, a locality that currently belongs to the municipality of Estopiñán del Castillo, in Huesca (Spain).^[7]

Deposits and uses

Aerinite from Spain

Aerinite is a rare mineral. It has been found in several deposits in the Spanish Pyrenees of Huesca and Lleida, as in Estopiñán del Castillo, Camporrélls, Juseu and Tartareu. In France, the site is important from St. Pendelon, in the Landes.^[8] Aerinite was used as a blue pigment in Romanesque paintings in many churches in the Spain, and also in some French, including the most famous of them, the Pantocrator in the church of San Clemente de Tahull.^[9]

See also

• List of minerals