Andesite has porphyritic structure and contains
hypidiomorphic phenocrysts of quartz (white), pyroxene (brown) and opaque minerals (black).
This white, medium-grained, equigranular, twomica granite exhibits
hypidiomorphic granular texture and is composed mainly of quartz, moderately altered perthitic potassium feldspar and plagioclase, and biotite (up to 20%), which is partially altered to chlorite.
The granite displays medium-grained,
hypidiomorphic to, less commonly, allotriomorphic, subequigranular to equigranular, and sparingly granophyric fabric.
The ores mainly comprise cataclastic, idiomorphic or
hypidiomorphic granular, and gric textures.
17) is a heterogranular,
hypidiomorphic, medium-to-coarse grain leucogranite (with a silica content normally over 75 %) in which its primary mineral constituents are quartz, feldspar, plagioclase and biotite.
The matrix has a poikiloophitic texture formed predominantly by plagioclase (labradorite, [An.sub.60-65], in some grains bytownite, [An.sub.70-75]) enclosed by elongated
hypidiomorphic brownish augite crystals of 0.3-0.8 mm length and isometric grains of subordinated olivine and biotite; accessory phases are apatite and magnetite.
Rock samples were found to be fresh to slightly weathered showing porphyritic to
hypidiomorphic texture.
On the basis of the relative proportions (volume %) of the three essential minerals, that is, perthitic alkali feldspar (50-55%), quartz (28-33%), and plagioclase (2-3%), these largely
hypidiomorphic and inequigranular to subequigranular rocks fall within the compositional field of alkali feldspar granite (Figure 2).
General appearance: Idiomorphic to
hypidiomorphic crystals up to 2 mm long and 0.4 mm thick.
Jijal ultramafic rocks are medium to coarse grained and have
hypidiomorphic texture whereas chromite mostly has allotriomorphic texture.
Petrographically identical samples of so-called "Silasia granite" were medium-grained biotite granite with allotriomorphic grains (quartz, feldspar) with the exception of biotite (
hypidiomorphic) and directionless structure.
Green crystals with xenomorphic and
hypidiomorphic habit (Fig.