Tantalo-silicate and titanate of Zr, Ca, Na. ZrO₂ = 29-32%. Anorthic. G = 3·2. H = 5. Colourless to yellow; transparent. Bohemia. ~Hellandite.~ 3H₂0, 2R´´O, 3R´´´₂O₃, 4SiO₂, where R´´ = Ca, Mg, Th/2; R´´´ = E, Al, Fe, Mn. E₂O₃ = 40%. Monoclinic; habit prismatic. G = 3·70. H = 5¹⁄₂. Reddish-brown when fresh. Lindvikskollan and Kragerö, Norway. Hiortdahlite. 3CaSiO₃,Ca(F,OH)NaZrO₃. ZrO₂ = 21·5; TiO₂ = 1·5%. Anorthic; habit tabular. G = 3·27; H = 5-5¹⁄₂. Yellow, with weak pleochroism. Island of Läven, Langesund Fiord, Norway. _Hjelmite_ (Hielmite). A stanno-tantalate of Ca, Mn, Fe, E, related to Yttrotantalite (_q.v._). E₂O₃ = 1-6%. Orthorhombic. G = 5·82. H = 5. Black; lustre metallic. Fahlun, Sweden. Homilite. (Ca,Fe)₃(BO)₂(SiO₄)₂. Sometimes with ceria earths, 0-2·6%. Monoclinic--isomorphous with Gadolinite (? Brögger). G = 3·34-3·38. H = 4¹⁄₂-5. Black; pleochroic. Islands of Lanegsund Fiord, Norway. _Hussakite_ (Xenotime). A prismatic form of Xenotime (_q.v._), erroneously supposed to contain > 6% SO₃. Diamond sands of Brazil. Hydrotitanite. An altered Perovskite (_q.v._) with Fe´´´ and aq. TiO₂ = 82·8%. Amorphous. G = 3·68. H = 1-2. Yellowish grey. Magnet Cove, Arkansas. ~Ilmenite.~ FeTiO₃; composition varies widely. TiO₂ = 3·5-52·3%. Rhombohedral. G = 4·5-5. H = 5-6. Black; opaque. Slightly magnetic. Norway; Dauphiné; Bohemia; Cornwall, etc. Ilmenorutile. FeO,Nb₂O₅,5TiO₂? TiO₂ = 66-75%. Tetragonal, very near to Rutile (_q.v._). G = 4·3-5·0. H = 6-7. Brown to black; opaque. Ilmen Mountains, Russia. _Johnstrupite._ Silico-titanate of E, Al, Mg, Ca, Na, etc., with F and aq. Cer = 13·5; Yttr = 1·1; TiO₂ = 7-8; ThO₂ + ZrO₂ = 3·6%. Monoclinic, very close to Epidote. G = 3·19-3·29. H = 5. Brownish green; weakly pleochroic. Islands of the Langesund Fiord, Norway. _Kainosite_ (Cenosite). CaY₂(SiO₃)₄,CaCO₃,2H₂O, where Y = Yttrium metals. Yttr = 30-37%. Uncertain; pseudo-hexagonal. G = 3·38-3·41. H = 5-6. Yellowish brown. Hitterö and province of Nordmark, Norway. ~Keilhauite~ (Yttrotitanite). An isomorphous mixture of Titanite (_q.v._) with (E,Al,Fe)SiO₅. E₂O₃ = 5-12; TiO₂ = 26-30%. Monoclinic; isomorphous with Titanite. G = 3·52-3·77. H = 6¹⁄₂. Brown to black. Various localities in Norway. _Kischtimite._ A fluocarbonate of the Cerium metals, near Parisite (_q.v._). Cer = 74·2%. Massive. G = 4·78. H = 4¹⁄₂. Yellowish brown; translucent. Barsovka River, Kyshtymsk, Urals. _Knopite._ A variety of Perovskite (_q.v._) containing E and Fe. Cer = 4-7; TiO₂ = 55%. Pseudo-cubic. G = 4·2. H = 5¹⁄₂. Grey; opaque; lustre metallic. Alnö, Sweden. _Kochelite._ A columbate of E, Fe, Zr; with ThO₂, SiO₂, Ca, aq., etc. Allied to Fergusonite (_q.v._). Yttr = 17·22; ZrO₂ = 12·8; ThO₂ = 1·23%. Doubtful; may be tetragonal.