a New Mercury Mineral frora Terlingua, Texas. 203 



There are no indications that the crystals are affected by tlie 

 light. If light affects the color it must act very slowly. The 

 color of those crystals, which are so situated as to have some 

 protection from the light, is exactly like that of the most 

 exposed. No difference in color could be noted between the 

 surface and the interior of the crystals. Most of the crystals 

 are translucent. The largest crystal found is brilliant and 

 transparent, and measures O'S™™ along its edge. Generally the 

 faces of tlie crystals are bright and uneven. They are very 

 brittle with signs of cleavage.* The fracture is uneven. The 

 hardness slightly exceeds that of calcite. The mineral crum- 

 bles to a powder under the pressure required for this test. No 

 piece could be obtained that was large enough to determine 

 the density. The luster is adamantine. The color is a rich 

 lemon- to a canary-yellow. The streak and powder are a very 

 pale yellow. 



When heated gradually to a low temperature in a closed 

 tube the assay turns to a dark reddish brown, almost black. 

 As the heat increases the color changes rapidly to white, but 

 without changing the form of the original crystals. Fumes of 

 calomel are given off and condense in the tube. Many glob- 

 ules of mercury collect in the tube beyond the coating of 

 calomel. Continued heating soon causes the assay to volatilize 

 and disappear. If a fresh fragment of the mineral is heated 

 rapidly in the closed tube, it decrepitates violently, almost 

 explosively, then it fuses and volatilizes. 



In cold hydrochloric acid the mineral is changed slowly to a 

 white substance which retains the original form. If the acid 

 is hot the change is more rapid but the product is the same. 



It is to be hoped that enough of the material will be found 

 to enable a complete analysis to be made. No doubt there 

 are specimens of this mineral in some of the collections, but 

 they are overlooked, or they are incorrectly labeled. The 

 second of the above-described specimens was labeled " Ter- 

 linguaite." It is more like kleinite in appearance. 



Chemistry ( W. F. Hillebrand). 



Chemically, so far as the very scanty material permitted of 

 ascertaining, the composition of mosesite approaches that of 

 kleinite, that is, it is a mercury-ammonium compound contain- 

 ing chlorine and the sulphate group besides a little water. 

 Determinations made on 0'04 gram of material gave 5 per cent 

 CI and 3'5 per cent SO^. The former amount is considerably 

 lower and the latter somewhat higher than in kleinite, but the 



* Imperfect octahedral cleavage (W, T. S.). 



