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Sect. VIII.j 



MINERALOGY. 



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«. Lead, giving a greenish yellow deposit. 



b. Zinc, having a white crust, which when heated becomes yellow- 



ish and difficult to volatilize. 



c. Antimony, a white deposit, easy to volatilize. 



d. Bismuth, a crust partly white, partly orange-yellow, without 



colouring the flame. 



e. Sulphur, with the well-known odonr of sulphurous aci(i 



/. Selenium, in an open glass tube, gives a red deposit «rf selenium. 

 g. Tellurium, in a similar glass tube^ gives a grayish-white erust of 



its oxide. 

 A. Arsenic gives off a grajish-white vapour, which 



garlic. 

 I. Quicksilver, in a^ glass tube, will be pi^cipitated^ in minute 



metallic globules. 

 k. Water, from hydrous minerals, deposited by condensation in the 



sanells 



same manner. 



flame 



4. 



directed upon the mineral ; whence may be distinguished 



a. Ked tint, given by several minerals contaiping strontia and 



(?) lithium. 



b. Green, produced by soiue phosphates and borates, sulphate of 



c. 



baryta, some copper ores and tellurium ores. 

 Blue, given by chloride of copper,, chloride of lead, &c. 



5th. The development of magnetic properties after treatment in the 

 reducing-flame, as in ores of iron, nickel, and cobalt. 



So far the assay has been considered by itself; bttt it is frequently 

 necessary to mix it with fluxes, either to render it fusible or to produc- 

 a glassy compound of a characteristic colour. 



Thus if boras or microcosmic salt be fused into a glass at the end of a 

 platinum wire bent into an eye, and a little powder of the unknown 

 mineral be added to it, we shall obtain by the use of the oxidizing fi 



the following results : 



Manganese, in all its compounds, gives a beautiful jiolet or amethyst 



colour. 



Cobalt causes a sapphire-blue colonr ; chromium an emerald-green. 



Oxide of iron produces a yellowish-red glass, which becomes paler as 

 it cools, and at length grows yellow or disappears, 



Oxide of cerium gives a red or dark-yellow colour, which ako grows 

 paler as it cools. 



Oxide of nickel renders the glass a brown or violet tint, which after 

 cooling becomes reddish-^brown, 



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