Loparite-(Ce)

Loparite-(Ce) is a granular, brittle oxide mineral of the perovskite class. It is black to dark grey and may appear grey to white in reflected light on polished thin section with reddish brown internal reflections.^[5] It has the chemical formula of (Ce,Na,Ca)(Ti,Nb)O₃.^[4] Nioboloparite is a variation of loparite-(Ce) containing niobium.^[6]

Loparite-(Ce)
General
Category	Oxide minerals
Formula	(Ce,Na,Ca)(Ti,Nb)O3
IMA symbol	Lop-Ce[1]
Strunz classification	4.CC.35
Crystal system	Loparit-(Ce)-Q: tetragonal[2] Loparit-(Ce)-O: orthorhombisch[2] Loparit-(Ce)-C: cubic[3]
Identification
Color	Black to grey-brown in thin section
Crystal habit	Cubic and octahedral crystals and massive
Twinning	Penetration twins common on [111]
Cleavage	[100] Imperfect
Fracture	Uneven
Tenacity	Brittle
Mohs scale hardness	5.5–6.0
Luster	Metallic to sub-metallic
Streak	Reddish brown
Diaphaneity	opaque, transparent in thin fragments
Specific gravity	4.60–4.89
Optical properties	Isotropic, anomalously anisotropic
Refractive index	n = 2.26–2.38
References	[4]

Loparite occurs as a primary phase in nepheline syenite intrusions and pegmatites. It is also found replacing perovskite in carbonatites.^[4]

Loparite was first described for an occurrence in the Khibiny and Lovozero massifs, Kola peninsula in northern Russia.

• Crystal structures of loparite
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Etymology

The term originates from the word Lopar, the former Russian name for the Sami indigenous inhabitants of the Kola peninsula, and the cerium content.^[4][5][6]