Danalite

Danalite is an iron beryllium silicate sulfide mineral with formula: Fe²⁺₄Be₃(SiO₄)₃S.

Danalite
General
Category	Tectosilicate minerals, feldspathoid group
Formula	Fe2+4Be3(SiO4)3S
IMA symbol	Dan[1]
Strunz classification	9.FB.10
Dana classification	76.02.04.02
Crystal system	Isometric
Crystal class	Hextetrahedral (43m) H-M symbol: (4 3m)
Space group	P43n
Identification
Color	Yellow, pink, reddish brown, red: colorless to pink in thin section
Crystal habit	Octahedral and dodecahedral crystals, typically massive or as segregations
Cleavage	{111} and {111}
Fracture	Subconchoidal to uneven
Tenacity	Brittle
Mohs scale hardness	5.5 to 6
Luster	Vitreous or greasy
Streak	Grey white
Diaphaneity	Semitransparent
Specific gravity	3.28 – 3.46
Optical properties	Isotropic
Refractive index	n = 1.747 – 1.771
References	[2][3][4]

It is a rare mineral which occurs in granites, tin bearing pegmatites, contact metamorphic skarns, gneisses and in hydrothermal deposits. It occurs in association with magnetite, garnet, fluorite, albite, cassiterite, pyrite, muscovite, arsenopyrite, quartz, and chlorite.^[2]

Danalite was first described in 1866 from a deposit in Essex County, Massachusetts and named for American mineralogist James Dwight Dana (1813–1895).^[4]

It has been found in Massachusetts, New Hampshire, Sierra County, New Mexico; Yavapai County, Arizona; Needlepoint Mountain, British Columbia; Walrus Island, James Bay, Quebec; Sweden; Cornwall, England; Imalka and Transbaikal, Russia; Kazakhstan; Somalia; Tasmania; Western Australia and Hiroshima Prefecture, Japan.^[2][3]