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ON THE CRYSTALLOGRAPHY OF ANATASE CRYSTALS FROM 
THE AURIFEROUS CONGLOMERATE OF THE WIT- 
WATERSRAND. 
By W. von Bonde, B.A. 
(Read August 19, 1914.) 
Dr. Robert B. Young, in a paper on Metasomatism in Banket," 
when describing a certain altered rock in the Rose Deep Gold Mine, 
South Reef Leader, says that the rock is composed mainly of chlorite and 
sericite, but when it is washed there remains a heavy concentrate com- 
posed of pyrite, anatase (octahedrite), zircon, chromite, and gold. 
Dr. Robert B. Young's description of the anatase crystals is as 
follows : — 
" The anatase does not occur as pseudomori^hs after r utile, hut as luell- 
formed tetragonal crystals, ivhich jnay he roughly descrihed as acute 
hipyramids. They vary in length from ahout f mm. to ahout one-sixth of 
that, the average lying midtuay hetiveefi these extremes. By reflected light 
they are a deep indigo -hlue in colour. The lustre is adamantine. In trans- 
mitted light they are most of them hlue. In polarised light they are 
pleochroic in different shades of hlue and yellow. Very many of the 
crystals are partially or wholly opaque.'' * 
A quantity of this anatase was obtained from Dr. Young and carefully 
examined by means of the Czapski Theodolite Goniometer (in its improved 
form),t fitted with a Schrauf signal. 
A preliminary general examination of the best crystals showed that 
the most prominent faces are those which together constitute the tetra- 
gonal bipyramid of the first order — probably (111). These faces present 
brilliantly reflecting surfaces. Next to these the most obvious form is the 
tetragonal bipyramid of the second order — probably (101) — capping the 
* Young, Trans. Geol. Soc. S.A., vol. xvii., p. 32. 
t Tutton, " Crystallography and Practical Crystal Measurement," p. 465, fig. 431. 
London, 1911. 
