PART I

_OCCURRENCE OF THE RARE EARTHS_

CHAPTER PAGE

I. THE NATURE OF THE MINERALS AND THEIR MODE OF OCCURRENCE 1

II. THE SILICATES 30

(_a_) _Silicates of Yttrium and Cerium Metals_--Cerite; Gadolinite, Glowing of Minerals; Allanite, Hellandite, Thalénite and Thortveitite; etc.

(_b_) _Silicates of Thorium and Zirconium_--Thorite, Zircon, Naegite; etc.

(_c_) _Mixed Silicates_--Eudialyte, Beckelite; etc.

III. THE TITANO-SILICATES AND TITANATES 52

(_a_) _Titano-silicates_--Yttrotitanite, Titanite; etc.

(_b_) _Titanates_--Yttrocrasite, Delorenzite, Ilmenite; etc.

IV. THE TANTALO-COLUMBATES 60

(_a_) _Containing no Titanium Dioxide_--Samarskite (Annerödite), Plumboniobite, Yttrotantalite, Fergusonite, Sipylite; etc.

(_b_) _Containing Titanium Dioxide_--Æschynite; the isodimorphous series Euxenite, Polycrase, Blomstrandine, Priorite; Risörite, Wiikite; etc.

V. THE OXIDES AND CARBONATES 72

(_a_) _Oxides_--Uraninite, Thorianite, Baddeleyite; Rutile, Anatase and Brookite; etc.

(_b_) _Carbonates_--Lanthanite; Parisite (Synchisite), Cordylite; etc.

VI. THE PHOSPHATES AND HALIDES 82

(_a_) _Phosphates_--Monazite, Xenotime (Hussakite); etc.

(_b_) _Halides_--Yttrocerite, Yttrofluorite; etc.

VII. THE MONAZITE SANDS 90

VIII. RADIOACTIVITY OF THE MINERALS 99