Ganophyllite

Ganophyllite
General
Category	Mineral
Formula (repeating unit)	(K,Na,Ca)2Mn8(Si,Al)12(O,OH)32 · 8H2O
IMA symbol	Gnp[1]
Strunz classification	09.EG.30
Dana classification	74.01.02.01
Crystal system	Monoclinic
Crystal class	Prismatic (2/m)
Space group	A2/a
Unit cell	22,545.01
Identification
Formula mass	1,514.2
Color	Brownish yellow to cinnamon brown
Crystal habit	Foliated micaceous
Cleavage	Perfect on {???}
Fracture	Brittle
Mohs scale hardness	4 - 4.5
Luster	Vitreous
Streak	Brownish yellow
Diaphaneity	Transparent to transculent
Specific gravity	2.84
Density	2.84
Optical properties	Biaxial(-)
Refractive index	nα = 1.537 nβ = 1.611 nγ = 1.613
Birefringence	0.076
Pleochroism	X = Pale yellow brown Y = Z = Dark yellow brown
Dispersion	Weak
Ultraviolet fluorescence	None
Common impurities	Fe, Zn, Pb, Ca, Ba
Other characteristics	Radioactive 3.87% (K)

Ganophyllite is a phyllosilicate mineral. It was named by Axel Hamberg in 1890 from the Greek words for leaf (φύλλον) and luster (γανωμα); the latter one was chosen due to the lustrous cleavages. The mineral was approved by the IMA in 1959, and it is a grandfathered mineral, meaning its name is still believed to refer to an existing species until this day.^[2] Tamaite is the calcium analogue, while eggletonite is the natrium analogue of said mineral.^[3]