VOL. XLIV.] PHILOSOPHICAL TKANSACTIONS. 325 



are called of the new rock. He then gives an instance of a turquoise which had 

 lost its colour on being laid by some time after its owner's death, which reco- 

 vered its beautifiil colour on our author's wearing it on his finger in a ring. 



Caesius, in his treatise de Mineralibus, p. 601, says, this stone is called Tur- 

 co'is by Mylius, in his Basilica Chemica; by Albertus Magnus, in his treatise ol 

 minerals ; and by Rueius, in his treatise of gems ; but Turca, by Caussinus de 

 Lapillis symbolicis. De Boodt, and Dr. Woodward,* with other modern writers, 

 take it for the callais of Pliny. Salmasius, in his Plinian. Exercit. p. 142, says, 

 many have mistaken the modern turquoise for the cyanus, but that the cyanus 

 was transparent like the sapphire; whereas the turquoise is a sort of jasper. 



Dr. Woodward, in his letter to Sir Jo. Hoskyns,-|- says, that the turcois, or 

 calla'is of Pliny, is nothing else but fossil ivory tinged with copper. It is not 

 denied, that some stones sold for turquoise, and possibly all that the Doctor saw 

 were certainly such ; but probably those which the authors call of the old rock, 

 and in which the colour is permanent, are real mineral stones : this sample now 

 produced seems to show this, both from the form and size; its shape shows it 

 not to be part of any animal bone; but its botryoid form is a demonstration 

 that it is the product of fire, which had once melted this substance; and that 

 when it cooled, its surface was formed into bubbles and blisters, in the same 

 manner as the haematitis botryoides or bloodstone, whose surface consists of 

 knobs, resembling a bunch of grapes. 



That the elephas tpuxTo;, or ebur fossile of Theophrastus, said| to be of va- 

 rious colours, thinks to be tinctured with copper, and to be what Dr. Woodward 

 calls the turquoise; indeed he suspects it to be what De Boodt calls of the new 

 rock, and says, is liable to lose its colour, which it recovers again from the 

 effluvia of the person who wears it. He therefore, for distinction sake, thinks 

 all these stones of the ivory origin should be called pseudo-turchesiae, or bastard 

 turquoise; and the other sort, of which this is one, the true or real turquoise; 

 for, by examination in the chemical way, he found it to be a very rich copper 

 ore; some of it pounded and dissolved in spirit of hartshorn gives a deep blue; in 

 aquafortis a fine green ; and an iron wire put into it was in 1 hour's time in- 

 crusted with copper; some of it calcined, without any flux in a crucible, run to 

 a slag, or half vitrified substance; whereas the same heat, had it been ivory or 

 bone, would have reduced it to a white ash like bone-ashes; for he exposed it to 

 such a fire as vitrified the tile that covered it. Its hardness and consistence to an 

 engraver's tool seems to be the same as common white marble; its colour is not 

 mended by heat, but it grows brittle when red-hot. 



• Method of Fossils. Letters, p. 17.— Orig. + ibid. p. l6.— Orig. 



} See Theophraatus's Hist, of Stones, translated by John Hill, Lond. 1746, 8vo. p. 94— Orig. 



