212 Kraus and Cook — Iodyrite from Tonopah. 



217. These crystals were apparently holohedral in their devel- 

 opment. 



The work of Seligmann was followed in 1885 by a descrip- 

 tion of crystals of iodyrite from Lake Valley, New Mexico, 

 by Genth and vom Rath.* Only three forms were noted by 

 them, but they describe an interesting type of twin crystal, 

 the individuals of which possess a rhombohedral development. 

 A plane parallel to a face of e\ 3034 \ acts as the twinning 

 plane. A twin of this character is reproduced by Dana.f 



The only other work on iodyrite up to the present time, 

 which has come to our knowledge, is that by Spencer J in 1901. 

 Spencer describes crystals from Broken Hill, New South 

 Wales. The simple crystals were tabular or short prismatic 

 and showed practically the same forms as observed by Selig- 

 mann on crystals from Chile ; see page 217. Spencer, however, 

 noted extremely interesting twins possessing a pseudo-cubical 

 development. These twins are interpreted by him as being 

 composed of four individuals of a trigonal character. The 

 twinning law is the same as that observed by Genth and vom 

 Rath, namely, 6J3034J. Repeated attempts were made by 

 Spencer to obtain etch figures but without success. 



Iodyrite from, Broken Hill, New South Wales. 



The crystals examined from this locality occur on a speci- 

 men of limonite and psilomelane, which was placed at our dis- 

 posal by the Foote Mineral Company of 

 Philadelphia, Pa. The crystals are very 

 small, being from 1 to 2 mm in length and 

 in all cases show an apparently holohedral 

 development. The color is a rather bright 

 lemon yellow. The faces are not nearly 

 as brilliant as those possessed by the crys- 

 tals from Tonopah, Nevada, which will be 

 described later. Although it was necessary 

 in making our readings to rely almost 

 entirely upon the maximum shimmer or 

 luster, we, nevertheless, feel that consider- 

 able confidence may be placed in the 

 results thus obtained. The following forms, _ 

 ojOOOl}, c'jOOOl}, m{1010\, « 1 1120 1, ^j 1011}, and u'\0£L\, 

 were definitely determined. Another form of a pyramidal 

 character was also noted, but our readings in this case were 

 somewhat unreliable so that we do not feel warranted in mak- 

 ing a statement as to its probable indices. The crystals possess 



* Zeitschr. Kryst., x, 473, 1885. 



f System of Mineralogy, 6th edition, 1892, 160. 



% Zeitschr. Kryst., xxxv, 460, 1901. 



