Davidite

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

• Davidite-(La) (La,Ce,Ca)(Y,U)(Ti,Fe³⁺
  )
  ₂₀O
  ₃₈ discovered at Radium Hill mine, South Australia in 1906 and named by Douglas Mawson for Australian geologist Tannatt William Edgeworth David (1858-1934).[6]
• Davidite-(Ce) (Ce,Le)(Y,U)(Ti,Fe³⁺
  )
  ₂₀O
  ₃₈ first described in 1960 from Vemork, Iveland, Norway.

Davidite-(La)
Davidite-(La) from Kazakhstan
General
Category	Oxide minerals
Formula (repeating unit)	(La,Ce,Ca)(Y,U)(Ti,Fe3+ ) 20O 38
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 [1]
Luster	Vitreous
Diaphaneity	Opaque, translucent in very thin fragments
Specific gravity	4.33 to 4.48
Alters to	Metamict
Other characteristics	Radioactive
References	[2][3][4][5]