Geikielite, the magnesium analogue of ilmenite, with the variety Picroilmenite, which is rich in iron.
Uhligite, a titanate of zirconium, calcium and aluminium.
Derbylite, Lewisite and Mauzeliite, an interesting series of titano-antimonates.
Warwickite, a boro-titanate.
CHAPTER IV
THE TANTALO-COLUMBATES
(a) Tantalo-Columbates containing no Titanium Dioxide
Samarskite, Yttro-ilmenite or Eytlandite (Urano-tantalite).
—Samarskite is a tantalo-columbate[59] of the rare earth metals, with iron, calcium, and uranium.
[59] In this and all similar minerals, columbium (niobium) and tantalum are to be regarded as vicarious; they replace each other in all proportions. It seldom happens that a pure columbate is found free from tantalum, or vice versa; one or other may predominate, but the two are almost always found together.