Calderite

Calderite is a mineral in the garnet group with the chemical formula (Mn²⁺, Ca)₃(Fe³⁺, Al)₂(SiO₄)₃.

Calderite
Calderite crystals on matrix from Sunndal Municipality Norway
General
Category	Silicate mineral
Formula	(Mn2+Ca)3(Fe3+Al)2(SiO4)3
IMA symbol	Cdr[1]
Strunz classification	9.AD.25 (10 ed) 8/A.08–40 (8 ed)
Dana classification	51.4.3a.6
Crystal system	Cubic
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Ia3d
Unit cell	a = 11.819 Å; Z = 8
Identification
Color	brownish red to brownish yellow
Cleavage	None
Mohs scale hardness	6.5–7.5
Luster	Vitreous
Streak	white
Diaphaneity	transparent to translucent
Specific gravity	3.756
Optical properties	Isotropic
Refractive index	n = 1.872
References	[2][3]

It is dark reddish brown to dark yellowish in color and generally granular massive in form.^[4]

It was named for geologist James Calder who worked on the geology of India. The name was first applied to a rock in manganese deposits in Katkamsandi, Hazaribagh district, Bihar and at Netra, Balaghat district, Madhya Pradesh, India. later transferred to its predominant mineral.^[3][4] In 1909 it was described as a mineral from Otjosondu, Otjozondjupa Region, Namibia.^[2]