﻿4:14 E. S. Dana — Crystallisation of Native Copper. 



The first important contribution to the subject is that of 

 Kose in 1837. He added to the planes before observed the 

 tetrahexahedron k (520, t-j-) and trisoctahedron m (311, 3-3), 

 both on crystals from the Ural. He also gives an interesting 

 description and explanation of the complex crystalline growths 

 afforded by the Siberian mines. He shows that in these forms 

 the branching takes place in the direction of the edges of an 

 octahedral face, that is, at angles of 60°, while the upper and 

 lower parts of the plates are in twinning position to each other. 

 The whole growth consequently forms a single twin, in which 

 the twinning-plane is the octahedral plane in which the 

 branches extend. Eose gives two large figures, projections 

 upon the octahedral twinning-plane which show clearly the 

 ideal relations of the parts of these complex forms. 



Levy about the same time (1837) described twin crystals 

 with e alone, and also with a, d, o and e ; he also mentions the 

 pseudo-hexagonal forms resulting from the distortion and twin- 

 ning of the tetrahexahedron e. Haidinger in 1863 described 

 peculiar hexagonal twins from Burra-Burra in Australia, formed 

 by a combination of the dodecahedron and cube. Schrauf in 

 1872 gave further obervations of the Australian copper, de- 

 scribing pentagonal dodecahedrons of the form e. In 1873 the 

 same writer figured a twin crystal of artificial copper in which 

 m (311, 3-3) was prominent. Zerrenner in 1874 mentioned a 

 crystal from Bolivia with e and t (421, 4-2), but gave no meas- 

 urements to support the latter form. 



Seligmann in 1876 described crystals from the Friedrichsse- 

 gen mine in Nassau showing pseudohexagonal symmetry, and 

 also twins with orthorhombic symmetry, not unlike forms from 

 Lake Superior explained on a later page. Jere'mejew in 1877 

 described crystals from the Altai with the form / (310, ^-3). 

 Gr. vom Eath in 1877 gave an interesting account of some Lake 

 Superior crystals with the new hexoctahedron y (18*10 *5, ^gM)-); 

 also of a complex combination of this form with the tetrahexa- 

 hedron h, showing a secondary growth of the first form on the 

 second. He gave, too, a brief account of a dendritic crystalline 

 growth analogous to the forms described by Eose. 



Fletcher in 1880 added the following new forms : h (410, ^-4), 

 e (730, i-H d (740, i-J), I (530, ^f), to (511, 5-5), p (411, 4-4), 

 and v (531, 5--|). Of these, Lake Superior specimens yielded 

 all except d and co. Lasaulx in 1882 described twin crystals of 

 copper from the Ohligerzug mine near Daaden, on the Sieg. 

 They were polysynthetic octahedral twins, in part with en- 

 closed twinning lamellae, and in part star-shaped, formed by 

 the grouping of five octahedral crystals about a common center. 

 A form similar to that last mentioned was described in 1883 

 by Foullon ; it was from Schneeberg, in Saxony. The most 



