Miarolitic cavities locally comprise up to 20% of the rock, and in places, contain the same hydrothermal mineral assemblage as the stockwork veins, including quartz, magnetite, chalcopyrite and trace bornite.
Unidirectional Solidification Textures, Miarolitic Cavities and Orbicles: Field Evidence for the Magmatic To Hydrothermal Transition in Intrusion-Related Mineral Deposits.
These miarolitic cavities
in the Pikes Peak granite get up to 4.5 meters deep, and one great microcline/quartz crystal plate in Adam's room measures about 20 X 60 cm; however, the prettiest pieces are miniature-size single crystals and tightly intergrown crystal clusters of fluorite, a few with shining, golden brown sprays and fans of acicular goethite crystals to 5 cm clinging onto their sides.
The presence of quartz and feldspar ph enocrysts, as well as miarolitic cavities
, requires the melt composition (the opposing end of the lever) to lie on the quartz- feldspar boundary line.
Also, the granite hosts the miarolitic cavities that have produced the collectible aquamarine, schorl and other interesting minerals.
The minerals listed below are primarily from the Erongo Mountains miarolitic cavities. However, for completeness, interesting minerals from pegmatites are also mentioned, because some of these pegmatites, notably the ones located close to the south, southwest and western side of the Erongo Mountains, are thought to be geologically related to the Erongo geological "event" (Pirajno, 1990).
There follows a chapter on the miarolitic cavities
that host the Baveno minerals, and a section describing all of the species reported from Baveno thus far, complete with ten SEM photos and 24 color photomicrographs that will make any micromount collector dream!
This beryl habit occurs in miarolitic cavities, in crystals replacing feldspar (Beyer, 1980).
It occurs there as blocky, fist-sized, euhedral crystals up to 15 cm in the miarolitic cavities in the granite.
The Zapot pegmatite is currently being mined for mineral specimens (chiefly amazonite, topaz and smoky quartz in miarolitic cavities
), for gemstones (topaz and smoky quartz) and for decorative rock (amazonite).
The miarolitic cavities
are flattened, round to oblong or freeform cavities, commonly 5-10 mm deep and 2-5 cm across.
The prospect intrusion is a small, differentiated dolerite laccolith containing shrinkage cavities and miarolitic cavities
lined with a variety of interesting minerals including prehnite, pectolite, analcime, albite and pyroxene.