Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/445

Rh MINERALOGY brown. Translucent in splinters. C.c. : niobic acid 49 -8, titanic acid 107, uranium oxide 237, protoxide of iron 3 &quot;3 lime 3 5 water 7 9. Nohl (Sweden). 686. POLYCUASF, 4RTi + Mb. Right prismatic (fig. 595). ooPoo, ooP (140), P, 2Poo (56). Fracture conchoidal. H. =5 to 6; G. =5 1. Black; streak grey- brown. B.B. decrepitates violently, incan descing, but does not fuse. Sol. in s. acid. C.c. : titanic acid 26 6, niobic acid 20 4, yttria 23 3, erbia 7 5, oxide of uranium 77, water 4. Hittero (Norway), Slettakra in Jb nkop- ing (Sweden). 687. EUXENITE, Right prismatic (fig. 596). ooP ( m ) 140; ooPoo (6) ; 2Poo (d) 52 ; P (p) 102 58. p : b 103 6. Fracture conchoidal. Opaque ; metallic to vitreous. Black and brownish black; streak red-brown. B. B. infusible. Not acted on by acids. C.c.: niobic acid 32, titanic acid 19 2, uranium oxide 19 &quot;5, yttria 18-2, cerium oxide 2 8, but variable. Jolster, Tromo, Alvo, &c., in Norway; also Hittero and Cape Lindesnaes. Fig. 596. 3 16 ; P (o : o) prismatic (fig. /f /TA 597 688. Right prismatic. ooP (J/) 128&quot; 34 ; 2Poo (y) 73 137 14 ; oo?3 69 23 ; Poo ; OP. Crystals long 597). Cl. traces ; fracture imperfect conchoidal. H. =5 to 5-5 ; G. -4 9 to 5 1. Opaque ; submetallic or resinous. Iron-black or brown ; streak yellow ish brown. B.B. swells and becomes yellow or brown, but is infusible. Not sol. in h. acid, partially in s. acid. C.c.: niobic and tT.talic acids 28 8, titanic acid 22 6, thorium oxide 157, cerium protoxide 18 5, lanthanum oxide and didymium oxide 5 6. Miask, Hittero. 689. POLYMIGNITE. Right prismatic. P (p) polar 136 28 and 116 22 ; ooP 109 46 ; oPoo ; oo Poo (fig. 598). Cl. macro-, Fi and brachydiagonal, imper- ^ sp feet ; fracture conchoidal. H. = 6 5 ; G. = 47 to 4 8. Opaque; semimetallic. Iron- black ; streak dark brown. B.B. infusible. Sol. in h. acid. C.c.: titanic acid 4 6 &quot;3, zir- conia 1 4 -1, yttria 1 1 -5, lime 4 -1, iron peroxide 12 &quot;2, cerium ox ide 5. Frederiks- varn. 690. MEXGITE, (Fe, Zr)T i. Right prisma tic. P (e} polar angle 151 27 and 101&quot; 10 ; ooP13620 ; ooP3; ooPoo (fig. 599). Fracture uneven. H. =5 to 5*5 ; 5 48. Opaque ; semimetallic. black ; streak chestnut-brown. infusible, but becomes magnetic. in s. acid. Miask, Groix island in Morbihan. 691. TANTALITE, Fe (a, & b). Right prismatic. P (p) with polar edges 126 and 112 middle 91 42 . ooPf (r) 122 53 oopoo (s}; ooPoo (t); Poo (m) 113 48; 3Poo (q) 54 10 ; |Poo (n) 167 36 ; |Pf (v) ; 2?2 (o). Fracture conchoidal or uneven. H. = 6 to 6 5; G. 6 1 to 8. Opaque; semimetallic, adamantine, or resinous. Iron-black ; streak cinnamon- or coffee-brown. B. B. infusible ; scarcely affected by acids. C.c.: 76 to 50 tan talic acid, 7 5 to 29 niobic acid, 9 to 16 iron protoxide, and 1 to 6 manganese protoxide ; some with 1 to 10 tin oxide (Cassitcrotantalite) ; also in union with iron (manganese) protoxide. Kimito and Tammela in Finland, Broddbo and Finbo near Falun, and Chanteloube near Limoges ; always in granite. 692. TAPIOLITE, 4Fea + FeSfb. Pyramidal. P middle angle 84 52, summit 123&quot; 1. H. = 6 ; G. = Fig. 598 (sp. 689). G. Iron- B.B. Sol. Fig. 599 (sp. 690). 30, Fig. 600. 427 ?i 2 o t0 r 5 ; ^ Ck i- Lu f/ ous - c - c - tantalic acid 73 -9, niobic acid [1 2, protoxide of iron 15. Tammela in Finland. 693. COLUMBITE, WiFeNb-MiFeia. Right prismatic. P (u) polar angles 104 10 and 151, middle angle 83 8 ; OP (c) ; ooPoo (b) ooPoo ; ooP ( g ) 135 40 ; ooPoo (m) 101 26 ; 2P (s) ; 3P3 (o) ; 3Pf (TT) ; JPw (7) 161 ; Poo (4) 143 ; 2Poo (h) 112 26 ; Poo (i) 101 12 ; 2Poo (e) 62 40 Hemitropes, face e; vertical axes forming an angle of 62 40 also on faces 2P2 (n), and rarely b. Also granular and foliated. Cl brachydiagonal, perfect, also macrodiagonal. H.=6; G. =5 4 to 6-4. Metallic, adamantine. Iron-black to brownish ; streak black Fig. 601. Fig. 602. Fig. 603. or reddish brown. B.B. infusible; not affected by acids. C.c.: isomorphic mixtures of niobic and tantalic acids with protoxide of iron (or manganese). Pure columbite would give 78 8 niobic acid, pure tautalite 86 tantalic acid. The niobic acid generally prevails, and the crystals are better formed the more this is the case. Rabenstein, Bodenmais, Chanteloube, Finland, Ilmen Hills, Evigtok in Greenland, Haddam and Middletown in Connecticut, Acworth in New Hampshire, Pike s Peak in Colorado. 694. YTTKOTANTALITE, (Y, Ca, Fe, Uy Ta, W, Nb). In two varieties, (a) Black. Right prismatic ; in short pris matic or tabular crystals, ooPoo ; ooP (m) 121 48. OP : 2Poo 103 26 ; Poo : OP 131 26 ; i : i 149 42 (fig. 604) ; also in grains and lamellae. Cl. brachydiagonal, indistinct; fracture conchoidal or uneven. Opaque, or in thin splinters translucent. Velvet-black, semi- metallic lustre, and greenish grey streak. H. -5-5; G. =5-4 to 57. (b) Yellow. Amorphous, yellowish brown, or yellow, often striped or spotted ; resinous or vitre ous ; streak white. G. -5 46 to 5 88. Both varieties B.B. infusible, but become _. brown or yellow. Not affected by acids. ^ C.c. : 57 to 60 tantalic acid, 1 to 8 tungstic acid, to 20 niobic acid, 20 to 38 yttria, 5 to 6 lime, 5 to 6 uranium peroxide, and - 5 to 3 5 iron peroxide. Ytterby, and near Falun. 695. FERGUSONITE, (Y, Er, Ce) 3 (Nb, Ta). Pyramidal and hemihedric ; P (s} 128 28 . Usual form (2), P, 4ooPf (g), OP (c) (fig. 605). s:s 100 54, s:c 115 16 , z: r 169 s 17. Cl. traces along P ; fracture imperfect conchoidal ; brittle. H.-5-5 to 6; G.=5 6 to 5 9. Translucent in thin splinters ; semimetallic. Brownish black ; streak pale brown. B. B. infusible. C.c. : chiefly niobic acid and yttria, with erbia, also a little cerium protoxide, tin oxide, ura nium oxide, and iron protoxide. Cape Fare well in Greenland, Ytterby, Riesengebirge, Rockport in Massachusetts. Tyrite, from Helle near Arendal, is similar. 696. HJELMITE. Massive, with granular fracture and traces *ig. 605. of crystals. H. 5; G. =5 82. Velvet-black; streak greyish black. Lustre metallic. C.c. : tantalic acid 62 - 4, tin 6 - 6, uranium 4 9, protoxide of iron 8 1, yttria 5 2. B.B. infusible. In closed tube decrepitates and yields water. Kararfvet near Falun. 697. SAMARSKITE (Uranotantalite.), (R 3) R,R8) 5 (&ba) :i. Right prismatic. ooP 122 46 ; ooP2 95; Poo 93; P; oopoc ; oo Poo ; 3 P| ; also in grains. Fracture conchoidal; brittle. H. = 5 56 ; G. =5 6 to 576. Opaque ; strong semimetallic. Velvet- black ; streak dark reddish brown. B. B. fuses on the edges to a black glass. In the closed tube decrepitates, yields water, incan desces, and becomes brown. Sol. in h. acid to a greenish fluid.