514 



MINERALOGY. 



Orjrctogno- Geofnostic and flrographic fH/uitioiis. Found, ac- 



.*^' ., cording to Hermann, in the land of the Kirguise, 125 



'"Y"^ leagues from the Russian frontier, where it is associ- 

 ated with fibrous and compact malachite, calcareous- 

 spar, and limestone. 



ORDER V. MICA. 



Order V. If no metallic lustre, the specific gravity is above 2.2. 

 MICA. Streak neither yellow nor dark-red. If the specific 

 gravity is under 2.2. the lustre is perfectly metallic and 

 shining. The cleavage is distinctly axifrangible and 

 prisimtoidal. The hardness varies from 1. to 2.5. 

 Specific gravity ranges from 1.9 to 5.6. 



This order contains seven genera, viz. 1. Copper- 

 mica; 2. Uran-mica; 3. Cobalt-mica; 4. Antimony- 

 mica; 5. Blue iron ; 6. Graphite; 7. Mica; 8. Pearl- 

 mica. 



fm GENUS. I. COPPER-MICA. 



MICA. Three axes. Cleavage prismatic. Streak green. 



Hardness = 2.0. Sp. gr. = 2.5. 2.6. 



This genus contains one species, viz. prismatic cop- 

 per mica. 



Prismatic 1. PRISMATIC COPPER-MICA, Jameson. Prismatis- 

 copper c her Kupferglimmer, Molts. Kupferglimmer, Werner. 

 Kici. Prism unknown. Cleavage prismatic. 



External Characters. Colour green. Occurs mas- 

 sive, disseminated, and in granular distinct concretions ; 

 seldom crystallized in very thin equiangular six-sided 

 tables, in which the alternate terminal planes are set on 

 obliquely. Externally smooth and splendent ; inter- 

 nally splendent, lustre pearly. Fracture small-grained, 

 uneven, inclining to conchoidal. Fragments intleter 

 minute angular and tabular. Massive varieties trans- 

 lucent ; crystallized transparent. Streak green. Sectile. 

 Rather brittle. 



ChemicalCharaclers. It decrepitates before the blow- 

 pipe ; and passes, first, to the state of a black spongy 

 scoria, after which it melts into a black globule, of a 

 slightly vitreous appearance. 



Conslit. Parts. Oxide of Copper, 58 

 Arsenic Acid, . 21 



Water, . 21 100 



Clienevix, Phil. Tr. 

 for 1801, p. 20). 



Geognostic and Geographic Situations It has been 



hitherto found only in veins in the copper-mines in 

 Cornwall. 



Mic*!! GtNUS IL URAN - MICA OR URANITE. 



One axis. Cleavage pyramidal. Streak green. Hard- 

 ness r= 2.0. 2.5. sp. gr. =3.1 3.3. 



This genus contains one species, viz. Pyramidal Uran- 

 ite. 



Pyramidal I.PYRAMIDALURANITE, Jameson. PyramidalerUran- 

 uranite. Glimmer, Mohs. Uran Glimmer, Werner. 



Pyramid = 95, 13'; 144 56'. The only distinct 

 cleavage is that parallel with the base of the prism. 



External Ckaraden. Chief colours green and yellow. 

 Seldom massive, sometimes in fkkes ; the massive va- 

 rieties are disposed in angulo-granular concretions. Fre- 

 quently crystallized. The secondary forms are the fol- 

 lowing : 



1 . Rectangular four-sided table, or short prism. Some- 

 times elongated. 2. The four-sided table bevelled on 

 the terminal planes, and the bevelling planes set on the 

 lateral planes. 3. The terminal edges of the table 

 truncated, thus forming an eight-sided table. 4. The 

 terminal planes of the four-sided table bevelled ; and 

 sometimes the edges of the bevelment truncated. 5. 



When the bevelling planes of No. 4. increase very much Oryctogn*. 

 in size, there is formed a very acute duuble four-sided s . v - 

 pyramid, in which tlie apices are more or less deeply ^^V"' 

 truncated 6. Sometimes the figure No. 4. is acumi- 

 nated on both extremities with four planes, which are 

 set on the lateral planes, and the apices of the acumi- 

 nations deeply truncated. 



Cry.-tals are small and very small, superimposed, and 

 form druses. Terminal planes of the table streaked, 

 but the lateral planes smooth. Externally it is usually 

 shining and sometimes splendent. Internally shining, 

 approaching to glistening ; lustre pearly. Transparent 

 and translucent. Streak green. Sectile. Not flexible. 

 Easily frangible. 



Chemical Characters. It decrepitates violently before 

 the blowpipe on charcoal ; loses about 33 per cent, by 

 ignition, and acquires a brass-yellow colour. 



Cornwall. 

 Conslit. Parts. Oxide of Uranium, with a 



trace of Oxide of Lead, 74.4 

 Oxide of Copper, . 8.2 

 Water, . . 15.4 



Loss, . . 2 100 



Gregor, in Annals of Phil. 



vol. v. p. 28k 



Geognoitic and Geographic Situations. Occurs in 

 veins in primitive rocks. In Cornwall in tinstone and 

 copper veins that transverse granite and clay-slate. 



Werner describes a soft mineral, found along with 

 Uranite, under the name Uran- Ochre. It does not ap- 

 pear to form a distinct species, nor can it be considered 

 as a subspecies of Uranite. It is here placed imme- 

 diatt ly after Uranite. 



* URAN- OCHRE, Jameson. Uran-Ocker, Werner. Uran-ochre. 



There are two kinds of this mineral, viz. Friable and 

 Indurated. 



1. FRIABLE URAN OCHRE, Jameson. Zerreibliche Friable 

 Uranocker, Werner. uran-ochre. 



External Characters.- Colour lemon- yellow, which 

 passes into straw-yellow and sulphuryellow, and also 

 into orange yellow. Occurs usually LS .1 coating or 

 efflorescence on pitch-ore, and sometimes small reniform. 

 Is friable, and composed of dull, dusty, and weakly co- 

 hering particles. Feels meagre. 



Geognoslic Situation, Occurs always on pitch-ore. 



K. INDURATED UUAN-OCHUE, Jameson. Feste Uran- Indurated 

 ocker, lYi-mer. uran-ochre. 



Exlrnial Characters. Colours are straw -yellow^ le- 

 mon-ycllow.andorange yellow; anci this lattcrpasses into 

 aurora-red and hyacinth-red, and reddish and yellowish 

 brown. Occurs uiassive diss-t mil rated, and supei imposed; 

 and sometimes a tendency to fibrous concretions. Inter- 

 nally glimmering, glistening, and resinous. Fracture 

 imperfect conchoidal. Opaque. Soft and very ?ot't. 

 Rather Sectile. Specific gravity, 3.1 SCO, La Mcthc- 

 rie. 3.2*38, Hailij. 



Chemical Characters. According to Klaproth, the 

 yellow varieties hre pure oxide of uranium, but the 

 brownish and reddish com > in also a little iron. 



Ge'ignostic anil Geographical Situations. It is found 

 at Joachim>thal, and Gottesgab in Bohemia, and at 

 Johanngeorgeni.tadt in Saxony. 



GENUS III. COBALT MICA, or RED COBALT. COBALT 



MICA. 

 Kobalt Glimmer, Mohs. 



Three axes. Cleavage prismatic. Streak red, green. 

 Hardness = 2-5. Sp. gr. = 4.4J. 



