COLLECTIONS IN ECONOMIC (JKOLOCJV AM) MHTALMIKCY. IKS 



Tbe model of tlif mine (lonsists nfL'fi plates of ^^la.ss set at «listaiices 

 ropreseiitinj; ."»<> I'eet apart. Upon these are drawn the outline of tln^ 

 siu't'aee ground, with the huildin^^s; the shafts, funnels, and wurkin;,' 

 spaces underuroiind ; and the ore bodies. l'>v lookin;; throii;,'h the plates 

 as they stand om* ean see represented tin* whole mine and itssurroiind- 

 in;js. It is eonstrnetedon a scale of Kio fret to the incdi. ((i(Jl.>(».) 



The operation of the furnace i.s illustrated by — 



vl) Averaj;o sanii»li' of himp ore " (Jnuiza." (filtyi.) 



(•2) Roasti'd (Jranza. (.')I(W2.} 



('.i) Coarse on» or " (Jranzifa." (.'>l(jr)7.) 



(4) Coarse Tierras or " (Jraiizita" roasted. (filB'i.^*.) 



(5) Fine ore or "Tierras." (r>ir>*i;{. ) 



((») Fine ore or "Tierras " roasted. (516'.*4.) 



(7) Wood, used for fuel. (51620.) 



(8) Soot, from coiidtiisers. (51()27.) 



(U) Acid water, from condensers. (51590.) 

 (10^ Miniature (jnicksilver flask. (51628.) 

 (II) Pure quicksilver. (51Wl».) 



ALUM 1 X I TTM. 



Aluminium Minerals. 



corundum. 



Composition: AI2O3. Sesqnioxide of aluminium containing aluminium 

 5.'i.4 per cent, and oxyjjen 40.(5 i)er cent., generally containing a small 

 amount of iron. 



It crystallizes in the rhombohe<lral system, prismatic and pyramidal 

 planes predominating. Large rough crystals are quite common. It 

 also occurs massive and granular. Its hardness is 0, being next to the 

 diamond. It varies in specific gravity from 3.00 to 4.10. It occurs in a 

 large variety of colors, esi)ecially redsand blues, and white. It is trana- 

 jiarent to translucent, and hasavitrons luster. Clear, transi)arent, red 

 corundum forms the gem, ruby, while the blue forms saphire. 



The most imjiortant use of corundum is for grinding jturposes, but 

 small amounts have been smelted direct for aluminium. Three illustra- 

 tions of corundum are shown here, and a full suit*' will be found with 

 tbe grinding and polishing materials. 



(1) Ronph crystal. Shimerville, Lehigh County, rennsylvania. (<W>57I?.^ 



(2) DecouiiiDsed rock, containing coninilnni. Shinierville, Lehigh County, Penn- 

 sylvaui.i. (<i»).'>74.) 



(:<) Luinj) corundinii. Al;il>ania. (i»(>.575.) 



HAUXITE. 



Composition: (AlFe)2()3 2H2(>. Ilydrated sesquioxiile of abiniiniM!;, 

 containing variable amounts of iron, silica and titanic acid arc also 

 generally ]>resent. Its general occurence is oiilitic and clay like. 

 iUll No. PJ 13 



