where it is an unmistakable product of metamorphism); and in metalliferous veins (Swarzenberg, Saxony).

Its igneous origin, at least in part, is proved by the appearance of similar products in slags of furnaces.

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53. Scapolite (Wernerite).-Dimetric. The crystals columnar, attached and imbedded, also clustered in geodes, or massive and granular. Cleavage prismatic, tolerably perfect. H.= 5-5.5. S.G. 2.6-2.7. Colourless, or coloured pale green, green, or reddish. Lustre vitreous to resinous. Semi-transparent to opaque. Cp. very fluctuating, in part answering to the formula: R3Si2+2ÄISi, with Ċa, Na, some H and Fe.

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Scapolite is an essential constituent of wernerite rock; it also occurs as an accessory in granite and other crystalline rocks, likewise in limestone, but in that case usually near the margin of intruded granites. Finally in veins of ore (Arendal).

Meionite and Mellilite.—Limpid crystals found in the marble blocks of Somma, and Mellilite, dirty yellow, found in nepheline rocks at Capo di Bove near Rome, are two minerals very closely allied to scapolite.

54. Epidote (Pistacite, Zoisite).—Monoclinic. Crystals columnar, extended in the direction of their horizontal axis, usually in geodes, also massive and in fibrous, granular, or compact aggregates. Cleavage orthodiagonal, very perfect, hemidomatic perfect. Fracture conchoidal to uneven. H.= 6-7. S.G. 3.2-3.5. Almost always coloured, viz. green, yellow or grey. Lustre vitreous, and on the cleavage surfaces adamantine. Transparent to opaque. Cp.=R3Si+2RSi, in which formula R=Ċa, with some Mg and up to 2 per cent H; R=Al, Fe. Bp. variable; after being subjected to strong heat or melted, all varieties may be decomposed by muriatic acid and they become gelatinised.

Zoisite is grey, with Ca and Äl; it occurs as an accessory in granular limestone and granite (Fichtelgebirge).

Pistacite is green and rich in Fe. It occurs as an accessory and very frequently in hornblende rocks, and is probably the product of decomposition of hornblende. It also occurs in beds of iron-ore (Arendal).

55. Orthite (Allanite, Cerine).—Monoclinic, isomorphous with epidote, but seldom occurs in distinct crystals. More usually massive, in granular and short fibrous aggregates. Fracture conchoidal to uneven. H.=5—5·6. S.G.=3·3—4.2. Colour, pitch-brown to black. Streak greyish or greenish. Lustre imperfect, metallic to vitreous and resinous. Translucent at the edges to opaque. Cp. variable. In part, R3Si+ RSi, in which R=Äl and R=Ċe, Ca, Mg, with little La and Ĥ, and in the variety orthite, Y. Bp. on charcoal, puffs up slightly and fuses to a black glass; with borax fuses easily and makes with oxidising flame a bead of blood-red colour in the heat and yellow on cooling; with the reduction flame the bead is green.

Orthite occurs as an accessory in granite, especially in certain narrow dykes of granite, rich in felspar, which traverse hornblendic rocks (Greenland, Dresden); in zirconsyenite (Hitteroë in Norway), where the crystals are a foot in height; sometimes in porphyries (Totun Fjeld in Norway).

56. Gadolinite.-Monoclinic, but seldom in crystals, usually massive and imbedded. Fracture conchoidal to uneven. H.= 6.5-7. S.G. 4 4.3.

Pitch- and raven-black. Streak

greenish-grey. Lustre vitreous, resinous. Translucent at the edges to opaque. Cp. various, in general R3Si; and R= Y, Ċe, Fe, Ca. Bp. puffs up slightly without fusing, glows vividly and burns to a light-grey colour. Gelatinises with

muriatic acid.

Gadolinite occurs chiefly in granite, and as an accessory, imbedded (Fahlun in Sweden, Hitteroë in Norway).

57. Axinite (Thumite).· Triclinic.

Crystals singly at

tached, or clustered in geodes, also massive, in scaly aggre

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gates. Cleavage indistinct. H.-6.5-7. S.G. 3.3. Colour clove-brown, grey, or plum-blue. Transparent to translucent at edges only. Exhibits trichroism in an eminent degree. Cp. very complicated R3Si+2RSi+BSi; and R = Ċa, Mg, K; R=Fe, Mn. Bp. melts easily, and with intumescence, to a dark green glass, which becomes black in the oxidation flame; with fluor-spar and sulphate of potash gives the reaction of boracic acid. After fusion it gelatinises completely with muriatic acid. Axinite occurs in the geodes of granite (Oisans, St. Gotthard), or in metalliferous veins (Botallack in Cornwall; Kongsberg in Norway).

58. Cordierite (Dichroite, Peliom, Iolite).-Trimetric. Crystals usually columnar, hexagonal, also massive and disseminated. Cleavage brachydiagonal, tolerably perfect. Fracture conchoidal to uneven. H. =7—7·5. S.G.=2·6. Colourless, but usually coloured bluish-grey, violet-blue, or brownish. Lustre vitreous; in fracture eminently resinous. Transparent to translucent, beautiful trichroism. Cp.=R3Si2+3ÄlSi; and R=Mg, Fe, Mn and H. Bp. fuses with difficulty at the edges to a glass; dissolved with difficulty in borax. Little affected by acids.

Cordierite occurs as a substitute for quartz, and an essential ingredient in several granites and in metamorphic gneiss, under circumstances pointing to an igneous origin, or to an origin from contact with igneous masses (Saxony). It also occurs in beautiful crystals in metalliferous veins (Bodenmais in Bavaria).

Fahlunite and Pinite are products of transmutation from cordierite, or (according to some authors) from nepheline. They occur porphyritically in granite.

Liebnerite and Oosite are like products. They occur chiefly in porphyry rocks.

C. TANTALATES (OR COLUMBATES) TITANATES,

VANADATES.

The minerals here grouped occur very frequently as accessory ingredients in plutonic and igneous rocks, and are for the most part of contemporaneous origin with the rocks in which they occur.

59. Pyrochlore.-Monometric, usually in octahedrons (crystals or grains imbedded.) Fracture conchoidal, brittle. H.= 5-5.5. S.G.=3.8-4.3. Colour dark reddish- and blackishbrown.

Streak light brown.

Lustre vitreous. Translucent

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at the edges to opaque. Cp. (Ca, Fe,Ċe, Mn) (Üb,Ti) with some NaF and H. Bp. becomes yellow and fuses with difficulty to a brown slag, previously (sometimes) emitting an intense light. When powdered, it is decomposed in concentrated sulphuric acid.

Pyrochlore occurs as an accessory in granite and syenite (imbedded), (Miask, Brevig in Norway), also in granular limestone (Kaiserstuhl in Baden).

60. Perofskite.-Monometric, usually in cubes or octahedrons. Crystals attached or imbedded, also massive. Cleavage cubal. H. 55. S.G.-4. Colour greyish- to iron-black, or reddishbrown. Streak greyish-white. Lustre metallic-adamantine. Opaque. Cp. CaTi, with small quantity of Fe. Bp. infusible. Scarcely affected by acids.

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Perofskite occurs as an accessory in chlorite schist (Slatoust, in the Ural) in talc schist (Zermatt), and in granular limestone (Kaiserstuhl).

61. Tantalite.-Trimetric.

Crystals usually columnar, also

Streak

massive and disseminated. Fracture conchoidal to uneven. H.=6—6.5. S.G.-7.1-7.9. Colour iron-black. brown. Lustre adamantine metallic. Opaque. Cp.

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(Fe, Mn) (Ta,Cb2), with sometimes some Ca and up to 16 per

cent. of Sn. Bp. unchanged. Not affected, or very little affected, by acids.

Tantalite occurs as an accessory in granite, imbedded, and is usually associated with beryl and tourmaline (Finland, Sweden). 62. Columbite (Niobite).-Trimetric, usually in thick tabular or broad columnar crystals. Cleavage macrodiagonal, very distinct, brachydiagonal distinct. Fracture conchoidal to uneven. H.-6. S.G. 5·4.-6·4. Colour brownish-black to iron-black. Streak reddish-brown to black. Lustre metallic adamantine. Opaque. Cp.= (Fe, Mn)3Üb2, with little Ca and Sn. Bp. infusible, unchanged. Not affected by acids.

Columbite occurs as an accessory in granite, associated with beryl and tourmaline (Bodenmais in Bavaria, Connecticut and Massachusetts), also imbedded in cryolite (Greenland).

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63. Wöhlerite.-Trimetric. Distinct crystals very rare, usually massive and disseminated. Fracture conchoidal. H.= 5.5. S.G. = 3.4, Colour wine-yellow to honey-yellow, or yellowish-brown. Lustre resinous in the fracture. Trans

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lucent. Cp. a silicate of Ca, Na, Ta, Zr. Bp. at first unchanged, after some time fuses to a yellow glass. Decomposes in concentrated muriatic acid.

Wöhlerite occurs as an accessory in zirconsyenite (Brevig in Norway), in syenite and miascite (Ditro in Transylvania). 64. Titanite (Sphene, Menochine ore).-Monoclinic, frequently crystallised, prisms and tabular, imbedded and attached, twins frequent, also massive and in scaly aggregates. Cleavage indistinct. H.=5—5.5. S.G. 34-3.56. Colour grey or

Lustre adamantine, often resinous. Semi-transparent to opaque. Cp.=2ĊaSi=ĊaTi3. Bp. fusible only at the edges. With microcosmic salt and metallic tin gives the reaction of titanium in the reduction flame. Incompletely decomposed by muriatic acid; completely decomposed by sulphuric acid, gypsum being formed.