PHYSIOGRAPHY. 



203 



Spinel. 



white. Streak white. Transparent . . . translucent, only 

 on the edges, if the color be very dark. 



Hardness =8-0. Sp. gr. =3-523, of a transparent va- 

 riety, between cochineal-red and carmine-red. 



Compound Varieties. Twin-crystals, face of composi- 

 tion parallel, axis of revolution perpendicular to a face of 

 the octahedron. Sometimes parallel to several faces of the 

 octahedron. 



1. The red varieties, exposed to heat, become black andopake; on 

 cooling they appear first green, then almost colorless, and at last, reas- 

 sume their red color. With borax, they fuse with difficulty, with salt 

 of phosphorus a little more easily. The dark colored varieties yield a 

 deep green globule. Spinel assumes positive electricity by friction. 



2. Analysis. 



- Silica. Ma s ? ne ' 



* of 



Analysts. Varieties and localities. J 



BERZELIUS. Blue, Aken. - 72-250 - 5-450 - 14-830 - 4-260 



KLAPROTH. Red. -74-500-15-500- 8-250- 1-500 



DESCOTILS. Gr 6 ^ 8 ^ 1 ^ ^ . 68 000 - 2-000 - 12-000 - 16-000 - 0-000 - 98-00 

 THOMSON. Gree ,? Hamburg, ? . 73.308 - 5.620 - 13-622 - 



Lime. Total. 



- 0-000 - 96-58 



- 0-750 - 98-50 



THOMSON. 

 ABICH. 



ABICH. 



(N. J.) 



Black, Amity, 



(N. Y.) 



Black, Vesuvius. 

 Red! Ceylon. 



- 61-788 - 5-596 - 17-868 - 



- 67-460 - 2-380 - 25-950 - 



- 69 010 - 2-020 - 26-210 - 



$ 7-420 ; 

 ( protox. \ 

 \ 16-564 ; 

 \ protox. \ 

 \ 5-060 , 

 I protox. < 



- trace - 99-98 



- 2-804 - 98-72 



- 1-100-100-00 



c MOO ; 



0-710 - < protox. 

 ( chrome. 



3. Crystals from Ceylon and from several places in the United States, 

 occur imbedded in white limestone. It is found also in veins with Cal- 

 careous Spar in serpentine, and in gneiss. Other varieties belong to 

 druses in volcanic rocks. Besides which, it is found abundantly in more 

 recent deposits, formed by diluvial or alluvial action, along with crystals 

 of Corundum, Zircon and other gems. 



4. The red, transparent crystals are almost exclusively brought from 

 Ceylon, where they occur in the sand of rivers. In Sadermanland in 

 Sweden, bluish and pearl-grey varieties occur imbedded in granular 

 limestone. Dark colored crystals, called Pleonaste, are found in Ceylon 

 in sand, and in implanted crystals on Vesuvius. 



