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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

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