In composition identical with Johnstrupite (_q.v._). Isomeric with Johnstrupite (_q.v._). G = 2·93-3·03. H = 4. Reddish brown; translucent. Langesund Fiord, Norway. _Muromontite._ A variety of Allanite (_q.v._), rich in yttria earths and Be, but poor in Al and ceria earths. Cer = 9·1; Yttr = 37·1%. _See_ Allanite. G = 4·263. H = 7. Black to greenish black. Mauersberg, Erzgebirge, Saxony. ~Naegite.~ A silicate of Zr, ZrSiO₄, with E, Th, U, Cb, etc. ZrO₂ = 55·2; Yttr = 9·12; ThO₂ = 5·01%. Tetragonal; in globular aggregates. Gr = 4·091. H = 7¹⁄₂. Dark green or brown; dull. Gravel-tin of Japan. Narsarsukite. Na₆FeTi₂Si₁₂O₃₂F. TiO₂ = 14%. Tetragonal. Habit tabular. Gr = 2·75. H = 7-7¹⁄₂. Yellow to reddish-brown; pleochroic. Plain of Narsarsuk, Greenland. Neptunite. (K,Na)₂(Fe,Mg,Ca,)₂(Ti,Si)₄O₁₂. TiO₂ = 18%. Monoclinic. Habit prismatic. G = 3·23. H = 5¹⁄₂. Black, red in flakes. Translucent to opaque. Narsarsuk, Greenland. _Nivenite._ A variety of Cleveite (_q.v._), readily soluble in dilute acids. Cubic; crystallisation indistinct. G = 8·01. H = 5¹⁄₂. Velvet black; opaque. Bluffton, Llano Co., Texas. _Nohlite._ A variety of Samarskite (_q.v._) containing water (→ 4·6%). Massive, without cleavage. G = 5·04. H = 4¹⁄₂-5. Brownish black; opaque. Nohl, near Kongelf, Sweden. _Oerstedite._ A variety of Zircon (_q.v._), poor in SiO₂. ZrO₂ = 69%. Tetragonal; angles exactly those of Zircon. G = 3·629. H = 5¹⁄₂. Reddish-brown; adamantine lustre. Arendal, Norway. ~Orangite.~ ThSiO₄, usually with Fe, Ca, H₂O in traces. ThO₂ = 71·2-73·8%. Tetragonal. Habit prismatic. G = 5·19-5·40. H = 4¹⁄₂-5. Orange yellow; lustrous. _See under_ Thorite. ~Parisite.~ E₂CaF₂(CO₃)₃. Cer = 50·8-64·4; Yttr = 0-2·5%. Hexagonal. Habit pyramidal. G = 4·36. H = 4¹⁄₂. Yellow to red; transparent. Muso Valley, Columbia; Montana, U.S.A.; Greenland; Norway; the Urals, etc. Perovskite. CaTiO₃, with traces of Fe´´. TiO₂ = 58·9%. Pseudo-cubic? Optically biaxial. G = 4·017. H = 5¹⁄₂. Yellow; transparent to opaque. The Urals; Switzerland; Tyrol, etc. _Pilbarite._ PbO,UO₃,ThO₂,2SiO₂,2H₂0 + 2aq. ThO₂ = 31·3%. Cer and Yttr--traces. Amorphous. G = 4·4-4·7. H = 2¹⁄₂-3. Bright yellow; opaque. Pilbara goldfields, West Australia. _Pitchblende._ A mixture of oxides, chiefly UO₂ and UO₃, but without E₂O₃ or ThO₂. Amorphous. G = 5-6·5. H = 3-4. Black; resinous lustre. Bohemia; Cornwall; Carolina; Norway, etc. _Plumboniobite._ A variety of Samarskite (_q.v._) containing Pb; R´´₂Cb₂O₇, R´´´₄(Cb₂O₇)₃, where R´´ = Fe, Pb, Ca, UO, R´´´ = E, Al. Yttr = 14·3%. Massive, isotropic. G = 4·80-4·81. H = 5-5¹⁄₂. Dark brown to black. Morogoro, Uluguru Mountains, German E. Africa. ~Polycrase.~ A titano-columbate of E and U; Yttr = 19·5-32·5; TiO₂ = 25-33%. Cer and ThO₂ traces. Isomorphous with Euxenite.