I 
46 MUSEUM BULLETIN NO. 27. 
whose edge is the shorter diagonal, and which belong to a very steep 
four-faced cube. 
Other crystals on the same specimens are more complex; as be :>re, 
the dodecahedron is the main form, and its edges are tuncated by n(211), 
but there are also present the four-faced cube, g(320), and six-faced 
octahedron. The faces of the latter form are curved, rendering a deter- 
mination of the indices impossible. 
Perhaps the most interesting crystals occurring on these specimens, 
however, are those which exhibit the rare six-faced octahedron, u(853). 
This form occurs practically uncombined on the crystals, being accom- 
panied only by very minute faces of the dodecahedron and the four- 
faced cube g(320), as illustrated in Figure 14. The faces of the six- 
faced octahedron are usually striated parallel to their intersections with 
the dodecahedron; in other cases they are curved and the form of the 
crystal then approaches a sphere, whose surface is generally drusy. 
Garnet is apparently the only cubic mineral whose crystals have been 
observed to bear the form u(853), and, so far as the writers are aware, 
even with garnet it has only been recorded once previously. This was 
in the case of garnets from Rothenkopf , Tyrol, described by Cathrein, 1 who 
states that the crystals were combinations of (110), (211), and (321), 
with faces of the new form (853) lying in the zone (110:101) on both 
sides of the dodecahedron faces. 
In the case of the Union pit crystals, this rare six-faced octahedron 
is found, as already stated, practically as a simple form; crystals were 
selected whose faces yielded good single images, and the mean measured 
angles were found to agree closely with the calculated values, as follows: 
Angle 
Measured 
Calculated 
853 : 835 
16° 29*' 
16° 254' 
853 : 853 
35 02 
35 17 
853 : 583 
24 31 
24 44 1 
The rose-coloured garnets have diameters up to half a centimetre, 
but the more complex crystals and the simple six-faced octahedra are 
usually smaller than this. 
Andradite, both apple green and pale yellowish, is also found in the 
Union pit, but the crystals call for no special description. 
Southwark Pit . The grossular garnet in the Southwark pit is remark- 
able in that it is colourless and transparent; it forms granular, somewhat 
cavernous, crystalline masses, composed almost entirely of grossularite, 
with a little reddish-brown vesuvianite in prismatic crystals, and minute 
i Min. Mitth., 10, 55, 1888. 
