36 
MUSEUM BULLETIN NO. 27. 
Another habit is illustrated by Figures 11 and 12. In this type the 
crystals, elongated in the direction of the vertical axis, are tabular parallel 
to a(100), the usual dimensions being about 2 mm. by 4 mm. Their 
terminations are flatter than in the crystals described above, owing to 
the larger development of the forms t( 112), s(lll), and x(221) as com- 
pared with A(331). The basal plane is small but usually present. These 
crystals are, so far as noted, less common than the stouter types, and 
they frequently have a yellowish tint; they appear to favour the narrow 
fissures rather than the. irregular cavernous druses in the massive diop- 
side, and are also found implanted on the walls of fissures in the chromite 
where they are accompanied by later crystals of emerald-green vesuvia- 
nite. 
Tabular crystals with acute terminations are also found ; the prisms 
and hemi-pyramid A (331) are the only forms prominently displayed, 
and the basal plane is commonly absent. Figure 10 illustrates this type. 
Though twin crystals are not very abundant, a few were observed 
on the specimens collected. These are contact twins of the usual type 
and they are flattened parallel to the twin plane a (100) ; one of these, 
which was measured, is shown in Figure 13. 
White to Pale Lilac Diopside . 
This material is not well crystallized. Usually it forms platy 
masses which may have a surface measuring several square centimetres, 
with a thickness varying from that of paper up to 2 cm. ; the plates or 
blades are intergrown in the form of an irregular network, intersecting 
one another at all angles and in all planes. The cellular spaces of this 
network have been more or less filled by the later deposition of crystals 
of pale green andradite and clinochlore, less often vesuvianite, both 
lilac and yellowish, and minute white calcite prisms. Occasionally 
imperfect crystals are found on these specimens; these are in the form 
of blades, tabular parallel to a(100), which is heavily striated parallel 
with the vertical axis and bevelled by narrow faces of the forms f(310) 
and m(110) ; b(010) is small or absent. These crystals are comparatively 
large, measuring 1 cm. or more across the blades and several centimetres 
in length, and they are only slightly translucent. No crystals of this 
type were found showing terminations. 
Bright Honey-yellow Crystals, 
Small transparent crystals of a honey-yellow colour are fairly 
common at the Montreal chrome pit. They have the usual prismatic 
diopside habit; inspection indicated that no new or unusual forms were 
present, and the crystals were not measured. 
