ALU 



Species 2. Plume alum. — yllumcn nativum f. plumcfiiin, 

 Werner. — NaturlL-liLr f. fcdir aluun, Germ. 

 FjliJar iihiii, ii\ve<:d. — Fiutra^tig a/awn, Dan. 

 yllun lie plume, Fr. 



The colour of this fubftance is yellowiHi or greyifh white. 

 Its external lullrc is dull, but fometimcs glimmering, or even 

 little-fliining. It confills of flender irregular hair-fhapcd 

 fibres, either finglc or accumuUited, and llightly adherent 

 to each other ; is feldom ilalaftitic or amorphous. It is 

 vifually opaque, but fometimes alfo tranfparent or femitranf- 

 parent. It excites the fame tafte on the tongue as the pre- 

 ceding fptcies. 



It is found efflorefcing on bituminous fchiftus at Gottwig 

 in Auilria, on grey argillite in Carinthia, in clefts and ca- 

 verns on Stromboh, the Solfatara, the grotto of St. Ger- 

 mano, Mifeno, and other places in Italy. 



In IClaproth's Eflays is an analyfis of the native alum of 

 Mifeno, from which it appears, that lOO parts yield by 

 fimple folution and cryftallization 47 of perfeft alum, and 

 29 more by the addition of the neceflary quantity of pot- 

 alh, the remainder being fand with a little felenite, and a 

 fmall trace of oxydated iron. 



Species 3. Mountain butter. — Vltrlolum aliimen luty- 

 raceum, Werner. — Bergbutler, Germ. 



Its colour is of a more or kfs dun ifabella yellow, or 

 yellowiHi brown. It occurs amorphous commonly overlay- 

 ing the furface of aluminous fchiftus in lumps or clots. In- 

 ternally it is fhining, with a waxy luftre. At firft it is very 

 foft, but by expofure te the air it becomes of a middle 

 confidence, between crumbly and compafted, and is then of 

 a (Irait fhiver)'- fratlure. Its fragments are indeterminate, 

 blunt. Its diftinft concretions are fmall and fine granular. 

 It is tranfparent on the edges, and (lightly elaftic ; feels 

 fomewhat uncluous, and leaves on the tongue an acerbly 

 fweetilh alfringent tafle. 



It occurs in many places where the aluminous fchiftus is 

 plentiful, and expofcd to the air, as at Muflcaw in the Ober- 

 laufitz : is alfo found in Siberia. 



It has not yet been analyfed, but probably differs from the 

 preceding, in containing a larger proportion of clay and 

 iron ochre. 



II. Family. Earthy-saline. Tafte aluminous, very 

 little foluble in water. All the ores that belong to the third 

 family are occafionally found to have undergone a natural 

 change, fmiilar to what is produced in them by art at the 

 alum manufaftories ; in confequence of which they often 

 yield, by lixiviation, a variable proportion of alum, and exhi- 

 bit the fweetifh aftringent tafte pecuhar to this fait. I. 

 Upon the purely fulphureous ores or alum-ftone with its 

 varieties, this alteration feems to take place by the aftion 

 of fubterranean fire : alum is alfo probably formed in mere 

 -«arthy compounds of filex and alurnine, that contain no 

 fulphur when they overlie heated fulphureous flrata, by 

 which they are firft cracked and then penetrated with ful- 

 phureous acid vapours. Examples of both thefe occur in 

 Italy at La Tolfa, not far from Civita Vecchia, and the Sol- 

 fatara in the Neapolitan dominions ; from 1 00 parts of 

 which Bergman obtained by mere hxiviation eight parts of 

 perfeft alum. 2. The well known property of pyritoug 

 and pyrito-bituminous matters to heat, and afford vitriolic 

 falls by the combined aftion of air and moifture, may alfo be 

 traced, though in a (lighter degree, in the aluminous ores of 

 this defcription ; hence it is that the upper ftrata of the 

 fofter aluminous fchiftus, of the alum earth, and the ful- 

 phureous peats are occafionally inipregnated with alum. 

 The marftiy black foil of Arragon, that yields pure alum 

 by lixiviation (Bowles's Spain, p. 388.), appears to be of 

 this kiad ; alfo the aluminous turf of Helfinborg in Scania 



ALU 



(Bergm. Eff. vol. i. 353.) ; and a vein of black cartli in the 

 Shetland illands, containing alum and fulphated iron. Alum 

 is alfo extracted from foffil wood in Htfl'e, (Vogel. p. 322.) 

 Springs in the neiglibourhood of thefe ftrata fometimes hold 

 a little alum in fulution, as thofe near Halle (Chym. Ann. 

 1788. p. 224.) 



Family III. Earthy — no aluminous talle — not foluble 

 in water. 



Species 4. Alum-ftone. ArglUa alumlnarls TolfinJtsiWcrn. 

 yl/umcti Inp'uL caJcar. mlnerallzal. Wall. — Alaun- 

 Jhiii, alaunhakhjle'in. Germ. — /llunjla}, Sweed. 

 Alunrig ftecnher, Dan. — Pierre alununeufe de la 

 Tolfa. Pierre calca'ire alumirieiife, Fr. — P'uira 

 calclnofa nhitninofn, Ital. 

 Alum-ftone is greyi(h or yellowifti white, ifabella yellow, or 

 light fmoak grey ; amorphous. Its internal luftre is dull, fel- 

 dom ghmmering. Its frafture uneven, fplintery. Fragments 

 indeterminately (harp-cornered. It has diftinft corrchoidal 

 concretions, which might be miftaken for a fine fchiftofe 

 texture. Is (lightly tranfparent at the edges. Is half-hard 

 pafling into hard. Brittle, infipid, feels meagre ; and ad- 

 heres (lightly to the tongue. 



Its fp. grav. according to Kirwan, is 2.424. It has an 

 earthy fmcll, and when projeiled on a red hot iron it Liifes 

 and gives out a black' fmoak, a (light fulpliureous fmelK and 

 the refidue acquires a reddifli colour. According to Mon- 

 net's analyfis, it confiils of fulphur and clay, in nearly equal 

 proportions, together with a little iron and potafti. Berg- 

 man found it to contain about 43 iulphur and inflammable 

 matter, 35 alumine, and 22 lilex. 



It is found in maffes and veins running through argillace- 

 ous rocks at La Tolfa, in the Hates of the church, and in 

 the ore from which the Roman alum is prepared. A vol- 

 canic origin has been generally attributed to it, but appa- 

 rently without reafon, as the veins of La Tolfa have been 

 traced into the Apennines. It was formerly fuppofed to be 

 moftly calcareous,as is evident from the fynonims quoted above. 

 La Metherie (Theorie de la Terre, vol. ii. p. 215.) has 

 hazarded an opinion that it is principally alum fuperfaturated 

 with alumine, and therefore earthy and infoluble. This is a 

 notion which derives high probabiUty from the recent ana- 

 lyfis of this ore, by Vauquelin (An. de Chem. vol, xsii, 

 p. 275.) %vho obtained from it 



Alumine - - 43.92 

 Sulphuric acid 25. 

 Potaih - - 3.08 

 Water - - 4. 

 Silex - - - 24. 



lOO.CO 



A nmilar kind of ore has been difcovered in rocks near 

 Poliniere in Brittany. 



Species 5. Alum-flate. Alumirwtis fchijlus, alaunfchiefer. 

 Germ Alun Jiifer, Sweed Arduije alunu- 

 neufe, Fr. — Lavngna aluminofa, Ital Ttiruo 



pala, Hung. Ktuajf^owoi fchifer-, Ruff. 

 Of this there are two varieties. 



Var. I. Common alum-flate. Gemeiner alaunfchiefer. 



Germ. — Argilla aluminaris fchijlofa 'vulgaris^ 



Werner. 



Its colour is blui(h black, fometimes greyifh black. 



Amorphous, or in concentric balls imbedded in the ftrata. 



Its internal luftre is ghmmering, or dull. Frafture ftrait 



or curved flaty. It Hies when broken into broad (hivers, or 



trapezoidal fragments. Gives a grey itreak ; feels rather 



fmooth but meagre. Is foft, brittle, and but little tlaftic. 



Vai". 2. Shining aliun-flate Glanzender aLiunfchiefer^ 



Germ. — Argilla aluminaris fchijlofa nitida, Werner. 



It 



