58 



MINERALS AND GEOLOGY 



th- 



in spots or bands. (Infusible) : Calcedonic Quartz, including 

 the various Agates, &c. (No. 43). 



(c) Stony or pearly. Vitreous. White, grey, red, green, &c. Mostly 



in lamellar masses, which cleave easily in several directions, 

 presenting smooth and somewhat pearly cleavage-planes. 

 Fusible, but as a general rule not very easily : the point of a thin 

 splinter is soon rounded or vitrified, however, in a properly 

 sustained flame : The various Feldspars, including more 

 especially Orthoclase or Potash-Feldspar (No. 57) ; Albite or 

 Soda-Feldspar (No. 58) ; and Labradorite or Lime-Feldspar 

 (No. 60). 



(d) Vitreous. Greenish- white or pale-green. Mostly in botryoidal 



masses with crystalline surface. Easily fusible. Yielding a 

 little water in the bulb-tube : Prehnite (No* 67). 



(e) Dark or bright-red, brown, c. Mostly in rhombic dodecahedrons 



or in small rounded masses. Fusible. (Sp. gr. over 3.4) : 

 Garnet (No. 47). 



(/) Black or dark-brown. Mostly in triangular (and often broken) 

 prisms, or in acicular or fibrous groups. Easily fusible : 

 Tourmaline or Schorl (No. 46). 



(g) Black, brown, green, greenish- white or colourless. In small 

 crystals (mostly imbedded in crystalline limestone, or other- 

 wise in trap rocks), and also in cleavable and granular masses. 

 Fusible : Pyroxene (including Augite, &c.) No. 53; and also 

 Amphibole (including Hornblende, &c.) No. 52. 



Too soft to scratch glass. Easily scratched, or cut, by the point of a knife. 

 ( (a) White, grey, &c. Effervescing in cold acids. Infusible : 

 Calcite (No. 88). 



(b) White, brownish, &c. Effervescing only in heated acids. 



Infusible : Dolomite (No. 90) ; also Magnesite (No. 91). 



(c) Green, reddish-brown. Mostly in six-sided prisms with 



rounded edges. Infusible, or nearly so. (H = 5.0) : 

 Apatite (No. 103). 



(d) Violet-blue, green, greyish, &c. Mostly in cubes. Fusible : 



Fluor Spar (No. 106). 



(e) White, yellowish, greyish, pale-red, &c. Mostly in cleav- 



able masses. Very heavy (sp. gr. =4.4 4.7. Fusible, 

 but not easily, tinging the flame pale-green : Heavy 

 Spar (No. 96). 



(/) White, pale-blue, reddish, &c. Mostly in cleavable masses 

 or small crystals in limestone rocks. Fusible, tinging 

 the flame carmine red : Ce.lestine (No. 97). 



( (g) White, greyish, &c. Scratched by the nail. Fusible ; be- 

 coming at once opaque and dull white when held at the 

 edge of a candle-flame ; yielding a large amount of 

 water by ignition in the bulb-tube : Gypsum (No. 98). 



(h) White, greenish, green and brown, &c ; often mottled. 

 Very sectile, and more or less soapy to the touch : 

 Talc and Steatite (No. 82). Also Serpentine (No. 83). 



(i) Dark or light green, scaly or earthy : Chlorite. 



(k) Pearly-white, brown, black, &c. In leafy and scaly masses 

 with more or less pseudo-metallic lustre. Splitting into 

 thin plates : The various Micas, including more espe- 

 cially: Muscovite or Potash-Mica (So. 77), and Phlogo- 

 pite or Magnesia- Mica (No. 78). 



