148 Field Columbian Museum — Geology, Vol. III. 



LINARITE 

 EUREKA, UTAH 



FIGS. 2 AND 3. PLATE L 



Several specimens of linarite from Eureka, Utah, were obtained 

 from Maynard Bixby. Of these one specimen, Mus. No. M 9616, 

 was especially remarkable for its size and perfection. The linarite oc- 

 curs in this specimen as a single crystal attached to a siliceous matrix. 

 On casual inspection the crystal has the appearance of a nearly square 

 prism terminated by two dome planes. Measurement, however, 

 shows that the crystal is, as is usual with linarite, elongated in the 

 direction of the ortho-axis, the two apparent domes being the unit 

 prism. The length of the crystal in the direction of the ortho-axis 

 is 12 millimeters, and its width 6 millimeters. A re-entrant angle sug- 

 gested that the crystal was probably twinned upon the basal plane, 

 but as it was deemed undesirable to remove the crystal from its 

 matrix, no careful study of this feature could be made. The color of 

 the crystal is the deep azure-blue characteristic of linarite, and is so 

 deep as to make the crystal as a whole practically opaque. On an- 

 other specimen, Mus. No. M 9617, several smaller crystals occurred 

 which permitted removal for measurement with the reflecting goni- 

 ometer. The habit and attachment of some of these were the same 

 as those of the large crystal, while others showed a more nearly tabu- 

 lar habit. The crystal selected for goniometric measurement ex- 

 hibted the same habit as the large crystal and was 6 millimeters long 

 by 3 millimeters wide. Its orientation was determined by well- 

 marked cleavage parallel to the orthopinacoid. On this crystal in 

 the zone of orthodomes two forms new to linarite were determined. 

 These were 8 (10.0.9) and (S.o.io). Of these <£,(9.o.io) was the better 

 developed. The occurrence of the domes and base nearly at right 

 angles to a (100) gives the crystal a characteristically hexagonal 

 appearance when viewed in the direction of the ortho-axis. In 

 the pyramidal zone a new form f (323) was observed. Its deter- 

 mination was based on its occurrence in the zone mgr and the angle 

 f a m' = (323) A (Tio) = 52° 45'. It will be noted that this pyramid 

 occurs in the same zone with the unit dome 5 (Toi), and if this dome 

 had been present in the crystal, as is frequently the case with linarite, 

 a measurement would have been obtained of it in that zone. As a 

 matter of fact, however, the dome which actually occurs was outside 

 the zone mgr. This affords additional proof of the correctness of its 



