Coronadite

Coronadite is the lead endmember of the coronadite group, a family of tectomanganates with a 2 × 2 tunnel structure. The mineral was named after Francisco Vasquez de Coronado who was an explorer of southwest US. The name was made up by Waldemar Lindgren in 1905.^[2] It is chemically related to ferricoronadite, an Fe+3 analogue, as well as cryptomelane, hollandite, manjiroite and strontiomelane.

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  Polyhedral representation of the 2 × 2 tunnel structure of coronadite. The black atoms represent Pb.

coronadite
Coronadita
General
Category	hydroxides
Formula	Pb(Mn4+6Mn3+2)O16
IMA symbol	Cor[1]
Strunz classification	4/D.08-70
Dana classification	7.9.1.4
Crystal system	monoclinic
Space group	I2/m
Unit cell	a = 9.938, b = 2.8678, c = 9.834, Z = 1; β = 90.39° V = 280.26
Identification
Formula mass	933.55
Colour	dark grey to black
Crystal habit	botryoidal; fibrous
Mohs scale hardness	4.5–5
Luster	submetallic
Streak	brownish black
Diaphaneity	opaque
Density	5.44
Refractive index	2.72?
Pleochroism	brown-grey
Common impurities	Fe, Al