A. H. Means — New Mineral Occurrences from Utah. 125 



Art. IV. — Some New Mineral Occurrences from the Tin- 

 tic Distinct, Utah • by A. H. Means. 



The following; paper is a brief account of some of the work 

 clone at the Geological Laboratory of the Massachusetts Insti- 

 tute of Technology, in connection with the forthcoming U. S. 

 Geological Survey Report by Professor W. Lindgren upon 

 the Tintic Mining District of Utah. Several minerals hereto- 

 fore unreported in the district were found, together with one 

 not previously noted in the United States, and another which 

 is believed to be a new mineral species. 



Geockonite,* (?) 5PbS.Sb„S 3 . — This specimen comes from 

 the 300-foot level of the Colorado mine, and consists essentially 

 of galena, anglesite and cerussite, together with small amounts 

 of quartz, zincblende, chalcocite and covellite. In polished 

 section, upon etching with HC1 (1 : 1), fine fingering veinlets 

 of an unetched metallic mineral were seen in the galena. Some 

 of this unetched material gave an antimony test in closed tube 

 and a lead coating on coal, showing the mineral to be a sulph- 

 antimonite of lead. A specimen of stibnite was polished and 

 compared with the sulphantimonite of lead upon the possibil- 

 ity that the lead noted was due to adhering galena and not to 

 the mineral itself. Micro-chemical tests upon the two speci- 

 mens did not correspond however. The mineral gave the 

 following micro-chemical reactions which are typical of geo- 

 cronite : f 



HC1 (1 : 1), no reaction. HC1 (concentrated), instantly, bright 

 brown then iridescent. HN0 3 (concentrated), mineral blackens 

 with slight effervescence, and finally is covered by a white 

 coating. KOH, no reaction. KCJN", no reaction. 



The mineral was also compared with a sample of pure geo- 

 cronite with which it corresponded in chemical and physical 

 properties, leaving little doubt as to the identity of the mineral. 



Adamite,;): 4ZnO.As,0 5 .H 2 0. — This mineral comes from the 

 No. 3 shaft, Iron Blossom mine. The specimen consists princi- 

 pally of the limonite, upon which are greenish white tabular 

 crystals the majority of which form radiate groups and rosettes. 

 Under the microscope, the crystals were seen to be tabular in 

 form, showed parallel extinction and low birefringence, and 

 practically disappeared in a solution having refractive index of 

 1'73. In closed tube with dried soda and charcoal a strong 

 arsenic mirror was obtained. In closed tube alone water was 



* Dana's System of Mineralogy, 6th Edition, p. 143, 1911. 



f From a manual of micro-chemical tests, now in the press, by Joseph 

 Mtirdock of the Geological Department of Hai*vard University. 



% Determined independently, some months previous to the author's deter- 

 mination, by W. L. Whitehead of the Massachusetts Institute of Technology. 



Dana's System of Mineralogy, 6th Edition, p. 786, 1911. 



