Manganoeudialyte

Manganoeudialyte is an moderately rare mineral of the eudialyte group,^[2] with formula Na₁₄Ca₆Mn₃Zr₃Si₂[Si₂₄O₇₂(OH)₂]Cl₂·4H₂O. The formula given is one of the forms that can be given, based on the originally reported one, and shows dominance of silicon at both the M3 and M4 sites. As suggested by its name, it is the manganese-analogue of eudialyte.^[3][5]

Manganoeudialyte
Pink crystals and aggregates of the rare mineral manganoeudialyte (IMA 2009-039) from the type locality (Pedra Balao, Pocos de Caldas, Minas Gerais, Brazil).
General
Category	Cyclosilicates
Formula	Na14Ca6Mn3Zr3[Si26O72(OH)2]Cl2·4H2O
IMA symbol	Meud[1]
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) (same H-M symbol)
Space group	R3m
Unit cell	a = 14.25, c = 30.08 [Å] (approximated); Z = 3
Identification
Color	Pink to purple
Crystal habit	interstitial patches
Cleavage	None
Fracture	Uneven
Tenacity	Brittle
Mohs scale hardness	5–6
Luster	Vitreous
Streak	White
Diaphaneity	Transparent or translucent
Specific gravity	2.89–2.94 (measured)
Optical properties	Uniaxial (+)
Refractive index	nω = 1.60 nε = 1.61 (approximated)
Pleochroism	None
References	[2][3][4]

Occurrence and association

Manganoeudialyte was discovered in khibinites of the Poços de Caldas massif, Brazil.^[3] Associated minerals are aegirine, analcime, astrophyllite, cancrinite, fluorite, lamprophyllite, nepheline, potassium feldspar, rinkite, sodalite, and titanite.^[2]

Notes on chemistry

Impurities in manganoeudialyte include strontium, potassium, niobium, aluminium, fluorine, and minor hafnium, cerium, and lanthanum.^[2][3]