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The ooid grains feature diagenetic replacive dolomitization and dissolution vugs.
The matrix includes scattered crystals of pyrite and hematite and the rock is penetrated by complicated branching fractures and vugs.
The Randville dolomite and the Vulcan Iron Formation contain vugs of calcite scalenohedra, dolomite rhombohedra, pyrite cubes, and marcasite blades.
The ores are characterized by massive purple and green replacement fluorites, and by large crystals deposited in vugs.
Amethyst is currently being extracted from vugs and fissures in Triassic rhyolites in Champasak Province, and there may be further discoveries.
REE minerals occur mainly in vugs and as crystal coatings, suggesting late-stage crystallization from an incompatible element-rich fluid.
Millimetre--scale laminations, small centimetre-sized voids/ vugs and caves of up to tens of centimetres wide and 1 to 2 metres high are also predominantly conspicuously displayed on the outcrops (Figure 4).
This assumption is further endorsed by Hill and Darling (1997), who analyzed the fluid inclusions in sphalerite taken from vugs in the Balmat-Edwards district and found that the mineralizing fluids were possibly brines with approximately 20 weight percent [CaCl.
The mineral grains are extremely small (10-20 [micro]m is not unusual) and easiest to identify in vugs, veins, and amygdales.