MINERALOGY. 



515 



This genus contains erne species, viz. Prismatic Red 

 Cobalt. 



1. PRISMATIC REP COBALT. Jameson Prismatischer 

 Kobalt Glimmer, Muk*. 



Hrim unknown. Cleavage prismatoidal. 



This tpeeies is divided into three subspecies, viz. 

 Radiated Red Cobalt, Earthy Red Cobalt, and Slaggy 

 Red Cobalt. 



FIRST SUBSPECIES. 



RADIATED RED COBALT, or COBALT-BLOOM, Jameson. 

 Kobalt- bluthe, Werner. 



External Cliirnctert. Principal colour red ; rarely 

 greeniih-grey, and olive-green. Occurs mas-ive di- 

 seminated, often in membranes, small renitbrm, small 

 botryoidal ; also in stellular and scopifbrm radiated or 

 fibrous concretions, which are sometimes collected into 

 granular concretions ; it also occurs crysullizi-d. (. 

 Uls generally acicular or capillary, and scopilbrmly or 

 stellularly aggregated. Externally shining, passing 

 into "plendent. Intemill} shining and glistening, and 

 lustre pearly. Fragmi-nt splintery and wedge shaped. 

 More or lest translucent; sometimes translucent on 

 the edge*. Colour not changed in the streak. Rather 

 ectile. Easily frangible. 



Chemical Character*. Before the blowpipe it be- 

 comes grey, and emits an arsenical odour, and tinge* 

 borax glass blue. 



Constituent Parli. Cobalt. 39 



Arsenic Acid, 38 

 Water, 23 - 100 



BuMolz. in J. d. Min. t. 25. p. 158, 



Geognottic Situation Occur* in veins, in primitive, 

 transition, ami secondary rocks, along with various 

 metalliferous compounds. 



graphic Situation. Occur* in veins in secon- 

 dary rock* at Alva, in Stirlingshire ; in limestone of 

 the cosl formation in Linlithgowshire ; formerly in 

 mall veins in sandstone of the coal formation, along 

 with galena and blende, at Broughton, in Edinburgh; 

 in the Clifton lend-mine* near Tyndrum ; and at Dol- 

 coath in Cornwall. 



Enh y red 

 cobalt. "> 



SECOND SUBSPECIES. 



B\I r, or COBALT-CRUST. 

 a, H'tmer. 



Jameson. 



External Ckaraclen. Colour red. Seldom occurs 

 massive or disseminated, generally in velvety crusts, 

 and also small reniform and bolryoidnl Generally 

 friable, ard rnir.|.,i-il ct' ealy and dusty part clef, 

 which are feebly glimmering or dull. The massive 

 varieties have a fine earthy fracture. Fragment* inde- 

 t< nninate angular, and blunt t ry easily 



frangible. Very soft or friable. Sectile. Streak shin- 

 ing. Does not coil. 



THIRD SUBSPECIES. 

 SI.AGOV RED COBALT. Jameson. Schlackige Kobalt- 



i" red blutl:, 



Ejtcrniii is Colours muddy crimson red, 



and dark hyacinth- red, which passes into chesnut- 

 brown. Occurs in thin crusts, and sometimes roni- 

 fiirni. Externally smooth. Lustre shining and resin- 

 Pnetun coQchotdal Translucent. Hud and 

 brittle 



and Geographic Situation!. Occult in 



veins along with other cobaltic minerals, in the mine Oryctogno. 

 of Sophia, at Wittichen in Fnrstemberg. ._*?'_,. 



COBALT OCHRE. 



The Black, Brown, and Yellow Cobalt Ochres, and 

 other similar minerals, ought t<> be arranged together, 

 and form a particular order by themselves. In the 

 mean time, we place them beside the Red Cobalt, on 

 account of their being often associated in nature with 

 that mineral. 



I. BLACK COBALT OCHRE, Jameson. Schwarz Black c - 

 Erdkobold, IVerner. 



It is distinguished into Earthy Black Cobalt-ochre, 

 and indurated Black Cobalt ochre. 



a. EARTHY BLACK COBALT-OCHRE, Jameson. Earthy 

 Schwarzer Kobold Mulm, Werner. Cobalt oxide noire black c - 

 terreux, Hauu. bait ochre. 



Efteni'il Character*. Colour intermediate between 

 brownish and blackish-brown. Friable, and composed 

 of dull coarse particles, which soil very li'.tle. Streak 

 shining Meagre to the f -el Light. 



Chemical CJurvctert. Before t!ie blowpipe, it yields 

 a white arsenical vapour ; and it colours borax blue. 



b. INDURATED BL\CK COBALT.OCIIIIE, Jameson. Indurated 

 Fester Schwarz Erdkolxild, Wernf. b '" ck c - 



Character* Colour distinct bluish-black. 



Occurs massive, disseminated, in crusts, small botry. 

 oidal, snial 1 renitiirni, t'ruticose, moss-like, stalactitic, 

 corroded, spei-u'ar, and with pyramidal iiupru.ii-iims. 

 SooMtixDe* it occur* in thin utitl curved In-nelhir con. 

 cretions. -Surface fcel)ly .'lininienng. Fracture fine 

 earthy, sometimes passing into conchoidal. Fragments 



rminate angular, and blunt-edged. Opaque. 



^ shining an. I rr-inous. Very soft, approaching 



to soft. Soils lot-Ill y S<-. till-. Very easily frangible. 



)c gravity, 2.019 to i.J-35, Grlleri.Z.^M. lireit. 



Chemical Character*. Before the blowpipe it yields 

 an arsenical odour, and colours glass of borax smalt- 

 blue. 



Ctmtli ue nt Pnrtx. It is Mnodcnd as blacX oxide of 

 cob ilt, with arsenic and oxide of iron. 



Geognutlii- Siluaii"ii. Both Mirts u-u.dly occur to- 

 jrrtluT, and in the .-a;ue kind of re]xpsitory ; but the 

 finf is the rarest. They are to n.l sometimes in, 

 primitive mountains, but most frequently in secondary 

 mount 



tinlion. Ft is found nt Alderly Edge, 

 C'lu-sliire, in red sandstone; in si .te-elay in the penin- 

 sula of Howth near Dublin ; at Riegelsdorf in Hessia, 

 and in many other countries on the I'ontinent. 



It is used in the making of smalt, and affords 

 a good blue colour, but not s-> tine as that obtained 

 from gr. y cllt. Of the two kinds of black cobalt, 

 the compact is that winch affords the most esteemed 

 blue colour. 



II. BIIOWN CoBALT-O. HRE, Jamcs-m. Brauner Erd- Brown eo- 

 kobold, Wciner. bait ochre. 



External Characters Principal colour brown, grey, 

 and brownish-black. Occur* massi.i-. disseminated, 

 and sometime* very nmcli cracked. Internally dull. 

 Fracture fiiie earthy, approaching to coiiL-hoidul in the 

 large. Fragments indeterminate angular, and blunt- 

 edged. Opaque Streak sf.ining and resinood Very 

 suit. Scclile. Very easily frangible. Light, 



