

1819.] the Turquoise and the Calaite. 411 



have since procured another, which, although a little altered at 

 the surface, appears to have undergone the same change. 



c. In layers, and disseminated in an umber brown substance, 

 porous, and very hard, which I formerly took for a clay porphyry : 

 but which I have more lately ascertained to be an indurated clay 

 ironstone (verhdrteter Thoneisenstein). Meder called it a clay 

 slate, reposing on veins of quartz ; but the matrix in which that 

 variety of calaite is found, when treated by the blow-pipe, is 

 attracted by the magnet, which leaves no doubt about its nature. 



d. The rarest position of calaite in beds is in conchoidal sili- 

 ceous schistus (Lydian stone), in which we find likewise very 

 distinctly veins of quartz, but other veins are filled with layers 

 of calaite. A very interesting piece which serves as a proof of 

 this assertion may be seen in the fine collection of M. Wagner. 



Lustre. 



It is dull internally ; of a waxy lustre in some pieces of a sky 

 blue colour ; splendent in those which are intimately combined 

 with quartz. 



Fracture 



The fracture is compact or subconchoidal in the mamellated 

 pieces ; conchoidal in the blue, when the calaites occur in layers; 

 in other specimens the fracture is uneven and rough, especially in 

 some green varieties ; in others, jine scaly ; namely, in the 

 quartzy or vitreous calaite, especially in that which is formed in 

 the siliceous schistus when the veins of quartz are not completely 

 converted into calaites. 



Fragments. 



The fragments are indeterminate, often triangular with sharp 



edges. 



__ 

 Jransparcncu. 



It is commonly opaque, very rarely a little transparent on the 

 edges. 



Hardness. • 



It is hard, but not so much so as quartz, on which the sharp 

 fragments make some scratches, but are speedily blunted, leaving 

 a white powder. This is a very good way of distinguishing 

 calaite from malachite, muriate of copper, or scoriaceous copper 

 ore, which in some varieties approach a good deal to the blue or 

 the green of calaite, so that the Boukhares often sell them for 

 calaites. 



Calaite yields with difficulty to the knife, and gives a white 

 powder ; the ores of copper, malachite, muriate of copper, Sec. 

 yield easily to the knife, and give a green powder, little different 

 in colour from the mineral itself. 



The whitish decomposed pieces are friable, adhere strongly to 

 the tongue, and resemble exactly porcelain clay, sometimes snow- 

 white, or having a slight bluish tint. 



