272 On Selenide of Mercury from the Hartz. 



In this specimen and in others there are many spherical cavi- 

 ties, surrounded with sectors of polarized light, and also several 

 amorphous masses of matter, round which there is also polarized 

 light, indicating, as all the phamomena of the crystals do, that 

 the matter of the garnet must have been in a soft state, and 

 compressed by some force emanating from these cavities. 



In another specimen of garnet, a large fissure in its interior 

 is occupied with granular matter, which must have issued either 

 from a burst cavity containing a fluid or a gas, or both ; but 

 what is very interesting, and what I have never observed in 

 any other mineral, the matter has in several places formed cir- 

 cular crystals of singular beauty, some being very simple, and 

 others very composite. 



St. Leonard's College, St. Andrews, 

 December 11, 1852. 



XL. On Selenide of Mercury from the Hartz. 

 By Professor Rammelsberg*. 



PURE selenide of mercury was first met with by W. Tiemann, 

 some considerable time since, in an abandoned mine in 

 the neighbourhood of Zorge in the Hartz. He considered it 

 to be native selenium, but it was shown by Marx to contain 

 mercury. (See Schweigger's Journal, vol. liv. p. 223.) The other 

 minerals with which we are acquainted, in which both the sub- 

 stances in question are met with, contain also sulphur, for in- 

 stance, Onofrite from San Onofre in Mexico, or lead and copper, 

 as is the case with the other seleniferous species of the Hartz. 



Some little time since I received from M. Roemer, assessor of 

 mines in Clausthal, a mineral from the Charlotte mine at that 

 place, which he considered to be selenide of mercury, with the 

 request that I would submit it to examination. I have done 

 so, and the result completely bears out M. Roemer's supposi- 

 tion. It is massive, fine granular, blackish-gray, mixed with 

 quartz, and interspersed here and there with red oxide of iron. 



Heated in an open tube it gives off a strong odour of selenium, 

 and is completely volatilized, with the exception of a residue of 

 quartz, the interior of the tube being invested with a brownish- 

 red and a white sublimate, and also with a deposition of metallic 

 quicksilver. It is soluble only in aqua regia, and the solution, 

 when the substance operated upon is pure, is perfectly free from 

 sulphuric acid. 



The result obtained from an analysis by means of chlorine, 



* From Poggendorff's Annalen, vol. lxxxviii. p. 319; communicated by 

 W. G. Lettsom. 



