Nohlite and Vietinghofite, varieties of Samarskite.
Hjelmite and Kochelite, minerals closely related to Yttrotantalite and Fergusonite respectively.
Koppite, Loranskite, Microlite and Rogersite, complex tantalo-columbates containing elements of the cerium or yttrium groups.
(b) Tantalo-Columbates containing Titanium Dioxide
Æschynite.
—A columbate and titanate of the cerium metals, with thorium, calcium, iron, etc. From the results of an analysis on a specimen from Hitterö, Norway, Tschernik proposed the rather formidable formula
2(2Ce₂O₃,3TiO₂),4(ThO₂,TiO₂),Y₂(CbO₃)₆,3(CaO,TiO₂),3Fe(CbO₃)₂,Fe(TaO₃)₂,6TiO₂.
This can be simplified to Y(CbO₃)₃ + ThTiO₄ + 3⁄2TiO₂, in which Y represents rare earth metals partially replaced (2 atoms) by ferrous iron (3 atoms), whilst thorium can be partially replaced by (2 atoms of) ferrous iron or calcium. Strutt found it to contain the uranium-radium combination and helium.
The crystals are orthorhombic, holosymmetric; a : b : c = 0·4866 : 1 : 0·6737.
Common forms—brachy- and basal pinakoids b {010} and c {001}, prisms m {110} and r {120}, domes d {101} and v {021}, with pyramid o {111}.