6 MINERALS. 



(imllar incorporation. Staladite accretes with a cryftallinc cover^ 

 ing, in like manner as calculus; and no one will venture to fup- 

 polc that cryftals can exiil vyithoi^t fait, or deny that the earth is 

 cryftallized by falts. Their tranfparency is derived from their 

 ♦itomic^l conliruciion, and tlieir colour from metals. The A^alne 

 ot gems is according to their tranfparency, hanlnefs, perrnanency 

 and colour; and from their being the principal inftruments of hu- 

 man luxury, are often imitated by the frauds of trade, 



VITRIOL, the pt-oducl of alum, intimately allied to metal, is of 

 different appearance and figure according f:? the nature of the me- 

 tal, of v^fhich the moll frequent are Iron, C^pp^^i"? and Zinc; 

 fome therefore moll commonly become fnlphureous Pyrites, others 

 terrene Ochres. Different Pyrites alfume different ftj^ures, whofe 

 earth into which it is refoWeci is ufually denominated Ochre, which 

 when proceeding from Iron is yellow, and becomes red when 

 burnt ; when from Copper by acid is green, by alcali blue : fo that 

 flones which are yellow or red, are pincipally from Iron; thofe 

 which are green or blue, from Co:)}>er. Kach kind of Ochre, by 

 cryllallization, coagulates earths into Tophi. 



METALS are fopradecom pound, and confilt of Earth, Salt, and 

 Sulphur. Iron, whenever prefent, is often diffolyed by the ele- 

 ments; and when diir(>ived by vi'riolic fait and an ocraceous earth 

 precipitated, Iron by cryllallization cements earths into llones, and 

 abforbed is multiplied by metal, and ^o produces many times more 

 than it had primarily received. Vitriol ihignating in the fiifures of 

 rocks retaining water, when multiplied and precipitated by a long ^ 

 lapfe ot tiine, palfes jjUo a vein, which when opened tranfverfely. 

 and tilled up with a different earth, will forthwith change the me- 

 tallic vein into a different one ; as from Iron or Copper^ Lead often 

 becomes enriched with Silver, &c. For the fame vein, by variable 

 moditication, may abound in Alum, Vitriol, Arfenic, Sulphur;^ 

 Iron, Copper, Gold, Silver, Antimony, Lead, Zinc, orBifrnuth. 



|lOCKSj appearing like tfie prominent bones of the earth, are of 

 great bulk, folidiiy, and longevity ; compofed of land, gravel, opake 

 and diaphanous (\ones, with every where argillaceous and otten 

 talcofe fubftances intermixed ; and are at lengh cemented into more 

 " folid maifes, with a various and irregular mlKture of cryllals of 

 Q^iartz, Mica, and Spar. That'thefe are the offspring of time 

 and the ftrata of nature, no one will doubt, whofe cohllituent parts 

 are toevery one palpable. In thefe the metallurgill will difcaver, 

 the matrices of minerals, many-lhaped from thejr mixture, and 

 dive rfi tied in fire. 



PETRIFACTIONS are rather the parents than the produa of 

 liiarmoreous mountains, and may confiil of as many diyerfifications 



