Sonolite

Sonolite
Sonolite (in bottom left corner) with zincite and manganosite
General
Category	Silicate minerals
Formula (repeating unit)	Mn9(SiO4)4(OH,F)2
Strunz classification	9.AF.55
Dana classification	52.3.2d.3
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/b
Unit cell	a = 4.87 Å, b = 10.66 Å c = 14.28 Å β = 100.3°, Z = 2
Identification
Color	Red-orange, pinkish brown to dark brown Colorless in thin section
Twinning	Common, singular or lamellar on {101}
Mohs scale hardness	5.5
Luster	Vitreous, Dull
Diaphaneity	Transparent to translucent
Density	3.82–4.00 (measured)
Optical properties	Biaxial (-)
Refractive index	nα = 1.765 nβ = 1.778 nγ = 1.787
Birefringence	δ = 0.022
2V angle	75° to 82° (measured)
Dispersion	r > v
References

Sonolite is a mineral with formula Mn₉(SiO₄)₄(OH,F)₂. The mineral was discovered in 1960 in the Sono mine in Kyoto Prefecture, Japan. In 1963, it was identified as a new mineral and named after the Sono mine.

Sonolite is transparent to translucent and is red-orange, pinkish brown to dark brown in color and colorless in thin sections. The mineral has a granular habit or occurs as prismatic to anhedral crystals up to 2.5 cm (0.98 in). Sonolite is the manganese analogue of clinohumite, a dimorph of jerrygibbsite, and a member of the humite group.

The mineral occurs in metamorphosed manganese-rich deposits. Sonolite has been found in association with calcite, chlorite, franklinite, galaxite, manganosite, pyrochroite, rhodochrosite, tephroite, willemite, and zincite.

In 1960, Mayumi Yoshinaga was investigating alleghanyite and other manganese orthosilicates in Japan. He discovered a dull, red-brown mineral on the first level ore body of the Sono Mine, and later from a number of other sites. Using samples from ten locations in Japan and one in Taiwan, the mineral was described in 1963 and identified as a new mineral species. It was named sonolite after the mine in which it was first found and the name was approved by the International Mineralogical Association.

As of 2012^[update], sonolite has been found in Austria, France, Japan, Kyrgyzstan, Romania, Russia, Sweden, Switzerland, Taiwan, and the United States. The type material is held at Harvard University in Cambridge, Massachusetts, US.