This leads via the replacement of primary K-feldspar ( perthitic and non-perthitic microcline ) to the formation of plagioclase ( albite or oligoclase ) and in certain places also to the formation of myrmekite.
42.
Elbaite forms in igneous and metamorphic rocks and veins in association with lepidolite, microcline, and spodumene in granite pegmatites; with andalusite and biotite in schist; and with molybdenite and cassiterite in massive hydrothermal replacement deposits.
43.
It occurs in nepheline syenites and pegmatites in association with aegirine, nepheline, microcline, arfvedsonite, elpidite, loparite, eudialyte, astrophyllite, mangan-neptunite, lavenite, rinkite, apatite, titanite and ilmenite.
44.
A microscopic examination of the samples of feldspar intrusions in granite of the Cape have indicated that the large crystals of orthoclase feldspar have principal minerals of quartz, orthoclase, microcline, albite, epidote, and biotite.
45.
In an analysis of the greywacke it has fragments with 70 % quartz, 10 % to 15 % plagioclase and microcline feldspar, 2 % dark iron containing minerals, with carbon flakes, in a matrix of 10 to 20 % clay.
46.
The major collecting areas are on the west side of the mountain and they contain the usual assortment of smoky quartz and amazonite, although, like the Tarryalls, the amazonite is usually very pale and is most often grades into plain microcline.
47.
In the Sao Jose do Campestre Massif in Brazil, the syenogranite is a coarse-grained rock composed of microcline, quartz, hornblende, and rare clinopyroxene, together with allanite, as essential minerals ( Benjamin et al ., 1998 ).
48.
At high temperatures Na + and K + readily substitute for each other and so the minerals will form a solid solution, yet at low temperatures albite can only substitute a small amount of K + and the same applies for Na + in the microcline.
49.
The following minerals are also found in the veins of cleusonite; quartz, chlorite, calcite, albite, microcline, tourmaline, fluorapatite, zircon, ilmenite, hematite, titanite, pyrite, chalcopyrite, tennantite, rutile, crichtonite, monazite-( Ce ), and native gold.
50.
At the same locality it was found in alkaline pegmatite veins associated with clinobarylite, natrolite, aegirine, microcline, catapleiite, fluorapatite, titanite, fluorite, galena, sphalerite, annite, astrophyllite, lorenzenite, labuntsovite-Mn, kuzmenkoite-Mn, cerite-( Ce ), edingtonite, ilmenite and calcite.
