Van Name — Crystals of Crocoite from Tasmania. 339 



Art. XXVIII. — On Crystals of Crocoite from Tasmania; 

 by R. Gr. Yan Name. 



A recent addition to the Brush Mineral Collection of the 

 Sheffield Scientific School consists of a series of specimens of 

 crocoite from near Dundas, Tasmania, purchased from the 

 Foote Mineral Company of Philadelphia. These specimens, 

 which are interesting on account of the diversity of develop- 

 ment of the crystals and the unusual habit which many of them 

 show, include both separate crystals and groups attached to the 

 gangue. The latter is a cellular limonite more or less coated 

 and intermixed with a black oxide of manganese (wad), but 

 showing no trace of lead or chromium minerals other than the 

 crocoite. In the cavities of this material, which has evidently 

 come from a zone of oxidation, the crocoite crystals occur in 

 irregular groups or loosely adherent masses. 



Two distinct types of development are shown by the crys- 

 tals. The habit exhibited by the detached crystals, and by a 

 number of smaller individuals still in position upon the gangue, 

 is quite different from that illustrated by Palache* for crocoite 

 from this locality, and is not mentioned by Dauberf in his 

 detailed description of crocoite from Brazil, Siberia and the 

 Philippines. Typical specimens of this habit are characterized 

 by a remarkable elongation of the prismatic faces, the unit prism 

 being the predominant form, and giving the crystals a nearly 

 square cross-section, since mAW& /= 93° 41'. Four of the crys- 

 tals of this type are from 40 to 64 mm in length, with a diameter 

 measured across one of the prism faces of from 1 to 2 mm , and a 

 number of others, including several fragmentary crystals, have 

 a relative length only slightly less. The faces of the unit 

 prism are lightly striated longitudinally, but are in other 

 respects smooth and even with sharp and well-defined intersec- 

 tions, the whole development of the prism being generally 

 surprisingly regular. In all cases, as far as was observed, the 

 crystals are of uniform diameter throughout and show no 

 tendency to taper. The terminal faces upon the crystals of 

 this type usually show a high polish and give excellent reflec- 

 tions. They are chiefly domes, but the base c (001) and the 

 pyramid t (111) are often present though rarely prominent. 

 No doubly terminated crystals of this type were observed. 



With one exception all the faces observed were known forms, 

 of which the orthodome k (101) and the clinodome z (,011) are 

 the most persistent. The new form is a clinodome j (032), 

 which was found on but one crystal. 



* This Journal, i, 389, 1896. + Ber. Akad. Wien., xlii, 19, 1860. 



