164 PHYSIOGRAPHY. 



Red Zinc-Ore Rhomb Spar. 



1. Retinite, if rubbed in an isolated state, acquires negative electricity. 

 In the flame of a candle, it melts and takes fire with a particular odor. 

 It is partly soluble in alcohol, leaving behind an unctuous residue. 



2. Analysis. 



By HATCHETT. By BUCHOLZ. 



Vegetable resin . . 55 00 . . . 91-00 



Asphalt or bitumen . 42-00 . . . 9-00 



Earthy matter . . 3 00 . . . 0-00 



3. It has been found in the beds of earthy brown coal near Halle on 

 the Saale ; at Bovey in Devonshire, also in Upper Austria, Moravia, 

 &c. The variety from Halle very much resembles a vegetable resin. 

 The purer specimens frequently consist of alternating layers more or 

 less transparent, corresponding to the external shape, and commonly in- 

 cluding a cavity. Its Sp. gr. =1-079. 



REUSSIN. (See Bloedite.) 

 RHAETIZITE. (See Kyanite.) 

 RHODONITE. (See Manganese Spar.) 



RHOMB SPAR. Brachytypous Lime-Halo- 

 id e. MOHS. 



Primary form. Rhomboid. P on P =107 22'. 



Cleavage, highly perfect parallel with the primary form. 

 Fracture, often conchoidal, at right angles to the axis. 

 Surface, even, 'or rather rough. 



Lustre vitreous, sometimes inclining to pearly upon fa- 

 ces of cleavage. Color white or grey, generally inclining 

 to yellow ; also yellow and brown. Streak greyish-white. 

 Transparent . . . translucent. 



Brittle. Hardness =4-0 C 3-001, clove brown ) 

 ...4-5. Specific gravity = (3-112, pale yellow $ V ' 



Compound Varieties. Massive : composition granular, 

 individuals strongly coherent ; face of composition uneven 

 and rough. 



