NOTES ON VARIOUS MINERALS IN THE MUSEUM 



COLLECTION 



BY OLIVER CUMMINGS FARRINGTON AND EDWIN WARD 

 TILLOTSON, JR. 



ANGLES1TE 



TINTIC DISTRICT, UTAH 

 PLATES xlv and xlvi 



An especially fine series of crystallized anglesite, received from 

 Maynard Bixby, all from the Tintic District, Utah, and chiefly from 

 Eureka, afforded material for a study of the crystal habits of the 

 mineral. The specimens were the choicest of many that had been 

 collected by Mr. Bixby, and are probably, therefore, the best represen- 

 tation of the anglesite of the locality that has yet been obtained. 



The crystals occur almost wholly in cavities in galena, the cavities 

 as a rule having a diameter of from i to 4 inches. The galena shows 

 a coarse, granular structure as a rule. The crystals of anglesite occur- 

 ring in these cavities are for the most part colorless, but some are 

 white and several show a tinge of yellow, in some cases a deep canary 

 yellow ; others exhibit smoky or gray shades. As a rule the crystals 

 are nearly transparent, some completely so, but others show cloudings 

 which may be so abundant as to make the crystals practically opaque. 

 As is usual with anglesite, the lustre is highly adamantine in some 

 specimens, but in others more nearly vitreous. The crystals vary in 

 size from minute, lining druses, to one having a length of 4.5 centi- 

 meters (1^ inches). For the most part a length of about 8 milli- 

 meters may be considered descriptive of the size. The crystal planes 

 as a rule are well developed and afford fairly good measurements with 

 the reflecting goniometer. Not infrequently, however, the surfaces are 

 more or less uneven so that only broken reflections are obtained. 

 The planes of the different forms are as a rule uniform in lustre and 

 character of surface, with the exception of the macropinacoid, a (100), 

 which is nearly always characterized by being striated in the direction 

 of the vertical axis. It can usually be recognized by the naked eye 



131 



