A. J. Moses — Wew Mercury Minerals from Texas. 255 



Other Characters of Eglestonite. — Luster, brilliant adaman- 

 tine to resinous. Color, varying between brownish yellow 

 and yellowish brown but darkening quickly on exposure to 

 sunlight and becoming nearly black but retaining a high 

 luster. In powder, greenish yellow to canary yellow, becom- 

 ing quickly green and finally black on exposure to light. 

 Transparent if smooth-faced. Brittle and without observed 

 cleavage. Hardness between 2 and 3. Specific gravity by 

 direct weight of two carefully picked samples 8'327, as follows : 



I. II. 



Grams taken -2576 -4548 



Loss in water -0310 •0545 



Specific gravity _ 8*309 8*345 



Heated on charcoal, volatilizes completely without fusion 

 and forms a slight grayish sublimate. 



Heated in the closed tube, decrepitates, becomes orange-red, 

 evolves dense white fumes and deposits a white non-crj^stalline 

 sublimate which is slightly yellow hot, drives without fusing, 

 is soluble in nitric acid and gives the chlorine tests with cop- 

 per oxide. Later the orange-red residue volatilizes completely, 

 forming a mercury mirror beyond the ring of chloride. 



In dilute nitric acid the crystals become opaque and pinkish 

 white but retain their shape and there is a visible formation of 

 metallic mercury. On heating, the mercmw dissolves with 

 ejffervescence and the pinkish white residue is also slowly but 

 completely dissolved. 



In cold hydrochloric acid the crystals do not whiten but in 

 hot acid the surface becomes gray from metallic mercury, 

 which dissolves with a very slight effervescence. The greater 

 portion of the crystal is insoluble even in concentrated cold 

 acid. 



If hydrochloric acid is added during the dissolving in nitric 

 acid there is a heavy precipitate formed, but on heating this and 

 the opaque white residue dissolve quickly and comjDletely. 



Name of Eglestonite. — For this substance, an isometric and 

 hexoctahedral oxychloride of mercury, the nam^e Eglestonite is 

 proposed in honor of the late Prof. Thomas Egleston, founder 

 of the Columbia School of Mines and for many years professor 

 of mineralogy and metallurgy in Columbia University. 



2. Terlinguaite, a Monoclinic Oxychloride of Mercury. 



On the specimens which show the eglestonite there is gen- 

 erally found a bright sulphur-yellow material usually as an 

 agglomeration of imperfect striated crystals and less frequently 

 as doubly terminated crystals of not over one millimeter in 



