TAB. XLIL 



S I L E X quartzum. var. dodecaedrum. 

 Crystallized dodecdedral Quartz. 



Class 2. Earths. Order 1. Homogeneous. 

 Gen. 6. Silex. Spec. 1. Quartz. 



Div. Crystallized. Far. Dodecaedron with triangular faces. 

 Syn. Quartz. Bab. 80. 



Quartz-hyalin dodecaedre. P e Hauy, tab. 40. 



Cristal de roche dodecaedre. De Lisle, t. 2. 

 p. 70. 



The regular dodecaedral crystal of quartz is somewhat 

 rare. I at present know of no certain habitat for it in 

 Great Britain, excepting at Craig Lackart, about 3 miles 

 from Edinburgh, from whence I have an irregular group 

 given me by Dr. P. Murray, who gathered it himself. It 

 is evidently taken from a rock externally in a state of de- 

 composition, as its matrix is porous and mixed with red 

 oxide of iron. It is sometimes found at Bristol, and also on 

 the Lancashire iron ore or haematites, Bab. 80. I have 

 such specimens also on an iron ore from Devonshire. The 

 specimen here figured, I believe, is from Cader Idris in 

 North Wales, and seems to have been thrown off from the 



