Then, a progressive metamorphism in these rocks is marked by the passing of greenschist facies mineralogy [actinolite + chlorite + quartz + plagioclase (
albite) + epidote minerals [+ or -] muscovite [+ or -] calcite] to epidote-amphibolite facies mineralogy [hornblende + epidote minerals + quartz +
albite [+ or -] garnet], and finally to amphibolite facies mineralogy [hornblende + garnet + plagioclase [+ or -] quartz].
The bias of almost all of the PLS models was negative; only the bias of the PLS model of
albite for KBr pellets had a positive value.
Alvaro Lucio (alucio@matrix.com.br) had about a dozen miniature and small cabinet-size specimens of hydroxylherderite horn Virgem da Lapa, Minas Gerais, with lustrous, sharp, twinned crystals, color-zoned in pale violet and pale brown, to 4 X 8 cm, the matrix pieces showing attractive associations of sparkly white
albite crystals and muscovite rosettes.
We used synthetic components (MgO for Mg) and natural minerals (orthoclase for Si and K,
albite for Na, hematite for Fe, diopside for Ca and Mg, fluorite for F, rhodonite for Mn), as standards.
Although the BLP is locally deformed (Kontak 2004), the tantalite-bearing sample used for dating records no evidence of post-crystallization deformation and, instead, the tantalite grains formed a cluster of radiating euhedral crystals in a host of coarse
albite (Fig.
Na2O + K2O (8.8 wt%) and contains small amounts of diopside acmite and hypersthene in the CIPW norms that are dominated by
albite quartz and orthoclase.
In this case, an increase in characteristic quartz peak intensity and the presence of other relictic phases such as
albite was observed in the products so obtained.
However, the porosity of the PTP-4a granite depends on the (recalculated) amount of
albite (cf.
Datolite and prehnite are still present; however,
albite and calcite become more common, as do the zeolites heulandite and stilbite.
The mineralogy of the granite is composed of quartz, alkaline-plagioclase (0.97
albite), K-feldspar, muscovite and biotite.