TIN. 



and when the Phcenicians came into CornwaU, aud faw th s 

 meial in its ancient Oimy llnte, tbey called .t » the mud ; 

 a«d he,>cc. fume have faid, the name /m, in Cornu-Bmi(h 

 n-an i» derived. Some of tlic ancients called it plumbum 

 [ilbum, white lead, probably to dillinKuilh it from common 

 lead ; not knowing that it was radically another metal. 



This met.\l, aonominated Kicrcr.'T.-o; by the Greeks, and 

 ftannum by the Latins, feems to I'ave been known from the 

 moft remote ages. It is mentioned by Mofes ; fee Numb. 

 xxxi chap. 22. It was tranfported to the Laft from 

 Spain and Britain by the Phoenicians, with which nations 

 they are faid to have carried on a lucrative commerce. 

 Homer mentions it ; andbyAriftotle, the epithet Ki^.T.xov, or 

 Ce/tii-, is applied to it, indicating plainly the country from 

 which it was procured. See Tis-Trade of Britain. 



Tis-Slonf, in Mineralogy, is the moft common ore of tin, 

 and is nearly a pure oxyd of that metal. The colour is brown, 

 which paffes from a blacki(h-brown to black, and from a 

 red-brown to yellowilh and grcenifli-wliite. It occurs cryf- 

 tallized and amorphous, aiid in grains and rolled pieces, 

 varying from the magnitude of a grain of fand to that of 

 »" '^gff' "'' larg*^"^- 1 ""^ primitive form of the cryftal is a flat 

 oaohedron : the angles are 112° 10' and 67^50'. The 

 figure of the cryftals is fcldom perfed ; fometimes a reft- 

 angular prifm is inlerpofed between the pyramids that form 

 the oAohcdron. The edges and fummits of the cry Hals are 

 frequently bevelled or truncated, from which a great variety 

 of lecondary forms is derived. The cryilals are alfo fre- 



jidary 



quently united, forming compound cryftals or macles 

 indeed, fo numerous are tlie fccondary cryftals of tin, that 

 more than on." hundred and eighty forms of fingle cryftals 

 have been obferved, befides the compound cryftals, of which 

 there is a confiderable variety. The furface of the cryftals 

 is commonly fmooth and fplendent, but is fometimes 

 flreakod. The ftrufture is laminar, but the lamins are 

 rarely vifible. The frafture is uneven and imperfeftly con- 

 choidal, with a more or lefs ftiining and refinous luftre. 

 When the laminar ftruAure is difplaycd, the luftre is highly 

 fplendent. The cryftals are femi-tranfparent or opaque, 

 the darker colours being opaque, the lighter fometimes 

 nearly tranfparent ; and the intermediate (hades are only 

 tranflucent, or tranflucent at the edges. The ftreak is a 



freyi(h-%vhite. Tin-ftone is hard, fcarcely yielding to the 

 nife, and giving fparks with fteel. It is brittle and heavy. 

 The fpecific gravity varies from 6.759 ^" 6.970. 



Before the blowpipe it decrepitates, and becomes paler ; 

 when finely pounded and mixed with borax, it is reducible 

 on charcoal to the metallic ftate. 



Tin-ftone contains the following conftituent parts, ac- 

 cording to Klaproth. 



Tki 

 Oxygen 



Iron 

 Silex 



Some analyfes of tin-ftone give from two to three per cent. 

 of alumine. The tin-ftone of Cornwall, drefled in the com- 

 mon manner, is reckoned rich if it yield 65 per cent, of tin. 

 Tin-ftone may be diftinguifhed from wolfram by its fupe- 

 rior hardnefs, as it gives fparks with fteel ; but wolfram 

 yields ealily to the knife. The powder of tin-ftone is a 

 greyilh-white, that of wolfram a reddifti-brown. It is dif- 

 tinguifhed from blende by its fiiperior hardnefs, and its not 

 emitting a fulphurous odour when pounded. By its greater 

 fpccific gravity and luftre, it may be diftinguiftied from 

 garnet; and iromfchorl, by its colour, luftre, form, and higher 

 12 



fpecific gravity. This ore occurs in veins and beds, and dil'- 

 feminated in granite rocks. The veins interfeft rocks of 

 granite, gneifs, mica-flate, and flate : tin-ftone occurs alfo in 

 alluvial foil in the diftrifts that contain tin-veins. Sec 



SxUEAM-TVn. 



IVood-tin is a fpecies of tin-ftone, or oxyd of tin, found 

 with flream-tin in rolled pieces, which are wedge-ftiaped or 

 renifoi-m, and fometimes globular. The ftrufture is di- 

 vergingly fibrous, with concentric laminse ; and from the 

 fuppofed refemblance to the tranfverfe feftion of fine-grained 

 wood, it received its name. The colour is commonly hair- 

 brown or wood-brown, paffing into yellowifti-grey. The 

 luftre is glimmering or filky. It is opaque, hard, and 

 brittle : the fpecific gravity is 6.450. It is infufible before 

 the blowpipe, but is changed to a browni(h-red colour. 

 When ftrongly heated in a charcoal crucible, it yields about 

 75 p:r cent, of metallic tin. The conftituent parts are, ac- 

 cording to Vauquelin, 



Oxyd of tin - 91 



Oxyd of iron - 9 



In Cornwall, this ore is almoft always found with ftream- 

 tin, and never in veins : it is faid, however, to have been re- 

 cently met with in cellular quartz, but in very minute 

 pieces. It is one of the moft common ores of tin in Mexico, 

 and occurs in veins that traverfe a porphyritic trap, and 

 alfo in alluvial depofitions. In fome wood-tin, there is a 

 fmall, black, fmooth globule, from which, as from a centre, 

 the fibres diverge : this has received the name of bird's-eye 

 tin. Wood-tin, in its ftrufture and mode of formation, 

 probably bears a near analogy to the kidney-ftiaped hema- 

 tite iron-ore. 



Bell-metal Ore, Tin Pyrites, or Sulphuret of Tin, is an ex- 

 tremely rare ore of this metal, being found only in Corn- 

 wall, at Huel rock, in a vein accompanied with fulphuret 

 of zinc and iron. Its colour is fteel-grey, pafling into yel- 

 lowiih-white : it has a metallic luftre, and granular uneven 

 frafture : it yields eafily to the knife, and is brittle. The 

 fpecific gravity is 4.350. It fufes into a black flag before- 

 the blowpipe, exhaling at the time a fulphurous odour. 

 It communicates a yellow or green colour to borax. The 

 conftituent parts differ in different fpecimens ; according to 

 Klaproth, they are as under : 



Tin 



Copper - 

 Iron 

 Sulphur 

 Earthy matter 



34 



36 



3 



2 



26.50 



30- 

 12, 

 30.50 



99 



Klaproth obferves, that the darker varieties of this ore are 

 confiderably poorer in tin than the lighter, but the propor- 

 tion of iron increafes. 



jinalyfis of the Ores of Tin. — The analyfes in the dry way 

 were made by Klaproth in charcoal crucibles in the follow- 

 ing manner, in which the refults were always found to be 

 conftant. The ore was broken, and well cleaned from the 

 matrix. One hundred grains were introduced into the 

 cavity of a charcoal crucible, clofing its orifice with a 

 ftopper of charcoal. The charcoal crucible was then fitted 

 clofe into one of baked clay, and placed upon the forge- 

 hearth before the nozzle of the bellows. The contents in 

 the charcoal crucible were reduced to the metallic ftate by 

 expofing it to a ftrong blaft for half an hour. The button 

 of metafiic tin produced was a little blackifh on the fides, 



and 



