Arrangement of Minerals, 357 



Tabular View of an Arrangement of Min-erals founded upon 



Physical and Chemical Characters, 



(Concluded from p. 182.) 



B« Zlarthy llXineralss 

 Minerals in most cases composed of one earth or more, fre- 

 quently coloured by metallic oxides, especially those of 

 iron. 



Order I. MICA. 



Not metallic. Cleavage distinctly axotomous. Streak 

 white . . . green. Hardness = 1.0 — 4.5. Sp. gr. = 2.3 — 3.4. 

 Genus I. Mica. 

 Rhombohedral. Prismatic and Hemiprismatic. Streak white... 

 green. Hardness = 1.0 — 2.5. Sp. gr. = 2.7 — 3.0. 



1, Prismatic Mica or Talc. 2. Hemiprismatic or di-axial Mica, 

 (Common Mica). 3. Rhombohedral or mono-axial Mica. 



Genus H. Margarite {Pearl-Mica). 

 Rhombohedral. Hemiprismatic. Hardness = 3.5 — 4.5. Sp.gr 

 3.0... 3.1. 



1. Rhombohedral Margarite (Clintonite). 2. Hemiprismatic Mar- 

 garite {^Common Fearl-Mica). 3. Axotomous Margarite (Py- 

 rosmalite of Hausmann). 



Genus HI. Cronstedite {3Ielan€-Mica). 

 Rhombohedral. Streak dark leek-green. Hardness = 2.5. Sp. 

 gr. = 3.3 — 3.4. 



1. Rhombohedral Cronstedite. 



Genus IV. Hydromagnesite {Kuphone Mica). 

 Rhombohedral. Hardness = 2.0. Sp. gr. = 2.3 — 2.4. 

 1. Rhombohedral Hydromagnesite, 



Order II. GRAPHITE. 



Metallic, not metallic. Streak black or brown; streak 

 shining. Hardness = 0.5 — 2.0. Sp. gr. = 1.8 — 3.7. 



Genus I. Graphite. 

 Rhombohedral. Metallic. Hardness = 1.0 — 2.0. Sp. gr. = 

 1.8 — 2.1. 



1. Rhombohedral Graphite or Plumbago. 



Genus II. Manganese Froth. 

 Amorphous. Aspect imperfect metallic. Hardness = 0.5. Sp. 

 gr. =; 3.7i 



