The freshly exposed surfaces often contain as many as six different mercury minerals, ranging in habit from individual crystals to subhedral and anhedral
masses, and also intimate mixtures displaying various colors.
These are mostly very fine to finely crystalline with subhedral to anhedral
dolomite fabrics (Sibley and Gregg1987).
quartz (< 2.0 mm) occurs in some SC FDE lavas, showing an undulated extinction and sometimes reaction rims of acicular augite ([En.sub.44-47][Fs.sub.9-13][Wo.sub.43-45]; Table 6, Fig.
Type 2 consists of fine- to coarse-grained, anhedral
quartz, sericite, and calcite, with minor Fe-oxides.
This species is of very rare occurrence in the British Isles where it was then only known as minute anhedral
inclusions in other minerals and was quite unknown in Derbyshire.
Where the two key alteration minerals, pyrite and quartz, are present, they usually occur as anhedral
crystals, but when pyrite occurs on its own, it is typically sub-to euhedral, with crystals that can be as large as 5 mm and usually oriented perpendicular to the fracture walls.
The enstatite (En 90-92) is euhedral to subhedral while the olivine (Fo 91-93) is subhedral to anhedral
(Siddiqui et al., 1996).
([An.sub.36] to [An.sub.40,7]) Landry Brook pluton gabbro/quartz diorite f-g--c.fr subhedral, zoned ([An.sub.36] to [An.sub.40,7]) quartz monzodiorite/ m.g subhedral, zoned monzogranite ([An.sub.30,6] to [An.sub.49,3]) monzogranite f.g.-m.g subhedral, zoned ([An.sub.18,6] to [An.sub.33,3]) Dickie Brook pluton leucogabbro/quartz gabbro m.g.-c.g.
When dolomite relics persist, they occur as small anhedral
inclusions up to 20-30 [micro]m (Fig.
General appearance: A corroded, anhedral
grain 2 to 3 mm across.
Minerals comprise coarse-grained milky white subhedral to anhedral
quartz, sericite, muscovite (Figure 4(a)), and sparsely distributed minor coarse- to medium-grained, euhedral to subhedral pyrite.