*** Welcome to piglix ***

Davidite

Davidite-(La)
Davidite-(La)-35242.jpg
Davidite-(La) from Kazakhstan
General
Category Oxide minerals
Formula
(repeating unit)
(La,Ce,Ca)(Y,U)(Ti,Fe3+)20O38
Strunz classification 4.CC.40
Crystal system Trigonal
Crystal class Rhombohedral (3)
H-M symbol: (3)
Space group R3
Unit cell a = 10.376, c = 20.91 [Å]; Z = 3
Identification
Color Black
Fracture Subconchoidal to uneven
Tenacity Brittle
Mohs scale hardness ~6
Luster Vitreous
Diaphaneity Opaque, translucent in very thin fragments
Specific gravity 4.33 to 4.48
Alters to Metamict
References

Davidite is a rare earth oxide mineral with chemical end members La and Ce. It exists in two forms:


...
Wikipedia

...