Aluminoceladonite

Aluminoceladonite is a low-temperature potassium dioctahedral mica mineral which is an end-member in the illite-aluminoceladonite solid solution series. The chemical formula for aluminoceladonite is K(Mg,Fe²⁺)Al(Si₄O₁₀)(OH)₂.^[4]

Aluminoceladonite
Heulandite with aluminoceladonite inclusions from Nashik District, Maharashtra, India (Dimensions: 14.8 cm x 10.2 cm x 6.5 cm)
General
Category	Phyllosilicate minerals, dioctahedral mica group, celadonite subgroup
Formula	K(Mg,Fe2+)Al(Si4O10)(OH)2
IMA symbol	Acel[1]
Strunz classification	9.EC.15
Dana classification	71.02.02a.06d
Crystal system	Monoclinic
Crystal class	2/m
Identification
Color	Colorless when pure, green when ferrous iron-bearing
Fracture	Micaceous
Optical properties	Biaxial (-)
Birefringence	0.0190-0.0240
References	[2][3]

Occurrence

Aluminoceladonite is often referred to as a rare mineral, though its actual abundance may be underestimated due to difficulty of identification. Aluminoceladonite, along with other phyllosilicate minerals in the illite-aluminoceladonite solid solution series, has been observed mainly among finely dispersed, mostly inter-layer-deficient, aluminium-rich potassium-dioctahedral mica varieties occurring in sedimentary rocks.^[5]