boiling. The original quartz and chalcedony banding is sometimes partially destroyed by
recrystallization (Adams, 1920). This type of quartz can contain useful primary and
secondary fluid inclusions. Cockade texture is a primary depositional feature that is
confined to breccia zones, where rock fragments are surrounded by concentric crusts of
quartz (Fig. 7M) (Adams, 1920; Dong et al., 1995). This occurrence of quartz, which is
uncommon in the Veta Madre, can contain useful primary and secondary fluid inclusions.
Moss texture silica has an origin similar to that of colloform silica, except that it occurs
as isolated spheres rather than in continuous bands (Adams, 1920) (Fig. 7N), giving it an
appearance that is similar to moss vegetation (Dong et al., 1995). This texture is produced
by surface tension affects when silica gel nucleates on impurities suspended in solution.
This type of silica contains no useful fluid inclusions. Comb texture quartz (Fig. 7O) is a
primary depositional texture that was observed in a few samples. This texture is
characterized by coarse, imperfect, euhedral crystals growing into open space
perpendicular to the vein walls (Adams, 1920). This type of quartz often contains
numerous microfractures that contain secondary fluid inclusions (Bodnar et al., 1985).
The ghost-sphere texture is a replacement texture of fine grained, anhedral to spherical
crystals that is similar to moss texture when observed under the microscope with
uncrossed polars (Adams, 1920). However, under crossed polars this type of silica shows
a jigsaw texture (Fig. 7R). This type of silica contains no useful primary fluid inclusions,
but secondary inclusions may provide information concerning later conditions.
As noted previously, boiling has been linked to metal deposition in precious metal
systems (Buchanan, 1979; Roedder, 1984; Bodnar et al., 1985; Brown, 1986; Simmons
and Christenson, 1994; Andre-Mayer et al., 2002; Etoh et al., 2002), and many of the