175 



TAB. CCCXCIX. 



PLUMBUM carbono-muriatum. 

 Carbono-muriate of Lead. 



Class. 3. Metals. Ord. 



Gen. Lead. Spec. Carbono muriate. 



Syn. A New Variety of Lead Ore. Chenevix in Ni- 

 cholsons 4to Journal. 4. 219. Klaproth's Ana- 

 lyses , vol. 3. 



I feel highly gratified in the opportunity of elucidating this 

 rare substance, which does not seem to have been known to 

 be found, excepting in this country in the neighbourhood of 

 Cromford Level, near .Matlock, Derbyshire. It was first 

 discovered to be a new mineral by the discerning Count de 

 Bournon, who has a primitive crystal of it, and many excel- 

 lent sketches and memorandums made from our late good 

 friend the Hon. Charles Greville's superb collection, which 

 is now happily secured to this country in the British Mu- 

 seum, and from which we have selected the best specimens 

 for these figures. 



The crystal is a rectangular prism, whose planes are pa- 

 rallel to the nucleus, sometimes having a cubical proportion, 

 with the angles replaced by isosceles triangular planes, the 

 incidence of which upon the terminal face is ] 22°. See the 

 llueish figures on the left of the yellow crystal, which look 

 like regular cubo-octaedrons. In these the columnar edges 

 are a little rounded by small faces, which in some crystals 

 are so much enlarged as almost to obliterate the primitive 

 ones. The yellowish lengthened crystal has the first of 

 these faces enlarged so as to form a four-sided pyramid, 

 with only a minute vestige of the terminal primitive plane, 

 and the edges of the prism replaced by truncating planes 

 arger than the portion thev leave of the original faces. 



This substance has generally a glassy or gem-like lustre, 



