Notice of Greenockite, a New Mineral Species. 391 



inclining to adamantine. Semi-transparent to semi-trans- 

 lucent. Hardness, about 3.5. Specific gravity, 4.8. 



Chemical composition, — It is a proto-sulphuret of cadmium, 

 and itsformula is Cd S. 



Geographical and Geognostical Situations. — It occurs near 

 Bishopton in Renfrewshii'e, in aporphyritic and amygdaloidal 

 trap rock, containing crystals of felspar and amygdaloidal por- 

 tions of calcareous spar, green earth, &c. Cavities lined with 

 prehnite are often met with ; and the Greenockite is found 

 either superimposed on the botryoidal surface of that mineral, 

 or disseminated through its fibrous mass. 



History. — This mineral was first noticed as an undescribed 

 substance by Lord Greenock, in compliment to whom we 

 have named it Greenockite. We are informed by Mr Brown 

 of Lanfyne, that he has had specimens of it in his possession 

 for many years, and that in his collection it was arranged 

 among the zinc blendes. The Greenockite is a species of anew 

 genus (the 6th in number) of the 5th order of the 2d class 

 of the systematic aiTangement, which we intend soon to lay be- 

 fore ovu" readers, and of which a tabular view appears in our 

 present number. It is to be regretted that the limited num- 

 ber, and the small dimensions, of the specimens hitherto ob- 

 tained, do not admit of the characters of this beautiful and 

 interesting substance being very fully determined. The crystals 

 are short 6-sided prisms, with trvmcated 6-sided pyramidal ter- 

 minations ; and two pyramids of different degrees of acuteness 

 have been noticed. These prisms have, at first sight, much 

 the appearance of regular 6-sided prisms, but are probably 

 compound forms. The faces of the more acute pyramid are 

 transversely streaked. 



Mr Brooke of London, to whom we sent some of the crys- 

 tals for examination, has kindly sent us the following sketches 

 of two of the crystals, with the accompanying measurements 

 and remarks. He says, " the form appears to be a regular 

 6-sided prism, but I suspect that it is derived, like sulphate 

 of potash, from the intersection of three rhombic prisms. I 

 have mcasm-ed the broken crystal, and find the angles to be 

 v.ery nearly 



