408 Dr. Gotthelf Fischer's Essay on [Dec. 



journey. Those of the new rock are of a bad blue, and but little 

 valued ; as many of them as we choose may be obtained for little 

 money ; while for some years the king of Persia has forbid the 

 old rock to be dug, except for his own use." 



It appears to me astonishing that Reaumur did not subject 

 these oriental turquoises to an analysis, or at least to a compa- 

 rison with those of Simore, knowing that the ambassadors sent 

 by the king of Persia to Louis XIV. brought among their pre- 

 sents a great many turquoises, which appear to have been all 

 from the new rock, as their colour inclines to white. Reaumur 

 wished to explain every thing by the objects which the mines of 

 Languedoc furnished him with. 



If Haiiy, in his valuable work, seems fully to confirm the ideas 

 of Reaumur by saying : " On trouve des dents molaires ou 

 autres parties osseuses d'animaux, penetrees de molecules 

 cuivreuses, qui leur donnent une couleur bleue et quelquefois 

 d'un bleu-verdatre. Les premiers ont ete apportees de Turquie, 

 ce qui a fait donner a. cette substance le nom de turquoise," it is 

 not surprising that the calaite, the true stone which comes from 

 Persia, has not yet obtained a place in the systems of mine- 

 ralogy. 



Though Meder had very well characterized this substance, 

 though Agaphi had ascertained the nature of the place in which 

 it occurs, and though Lowitz had proved by analysis that the 

 oriental turquoise contains merely a trace of lime, and no phos- 

 phoric acid, Reuss has notwithstanding made it only a fossil, a 

 petrified substance. 



To avoid all confusion, I shall reserve for the stony turquoise 

 the name of calaite, given it by Pliny. This essay, therefore, 

 shall be divided into two chapters. In the first I shall treat of 

 a hardened clay, coloured by an oxide of copper, or an arseniate 

 of iron — a substance which must occupy a place in the oryctog- 

 nostic system. In the other I shall give an account of the fossils 

 which have been found changed into turquoises by the contact 

 of the requisite substances. 



Under these two points of view we must divide the authors 

 who have treated of the turquoise. 



Authors who have treated of the Calaite or the Stony Turquoise. 



Tavernier, J. B. Voyages en Turquie, en Perse et aux Indes, 

 a Paris, 1678. 4to. 



Boccone, intorno le Turchine o Turquoises della nova rocca. 

 Museo di Fisica. Observ. 43. p. 278. 



Meder et Lowitz, Notices employees par Reuss, Mineralogie 

 ii. th. b. iii. p. 511. 



Agaphi, Dmitrie, Etwas von der eigentlichen Beschaffenheit 

 des Orientalischen Turkis. See Pallas IVeueste Nordische Bey- 

 trage. B. i. p. 261. n. xiii. 



Bruckman in Orell's Annalen, 1799. B. ii. p. 185—199. 



