Porphyry is the name given to decorative granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass. The larger crystals are called phenocrysts. In its non-geologic, traditional use, the term porphyry usually refers to the purple-red form of this stone, valued for its appearance, but other colou… Webporphyry and epithermal deposits. The largest and richest gold-bearing, global porphyry systems are related to potassic magmas. About 60% of the gold that is contained in the …

Porphyry geological feature Britannica

WebRocks composed of a basis, through which are dispersed crystals, are called Porphyries; such as are said to belong to what is considered the oldest rock, are a … WebThe quartz feldspar porphyry is altered with feldspar replaced by sericite, biotite replaced by chlorite, while secondary K-feldspar occurs in groundmass (Figures 3(C)-3(c)). The andesite is pinkish dark green in color and associated with magnetite veinlets and K … dayleen intimates inc

The geochemistry and alteration of the White Devil porphyry ...

WebAn alkali-feldspar granite porphyry dike crosscuts the granite porphyry in the central- SW area and is equivalent to the andesitic dike described by Williams et al. (999). The dike (sample 34) has ... WebIn feldspar: Crystal structure. (A porphyry is an igneous rock containing conspicuous crystals, called phenocrysts, surrounded by a matrix of finer-grained minerals or glass or both.) In most rocks, both alkali and … WebQuartz-feldspar porphyry. Mineralogy of Quartz-feldspar porphyryHide. Essential minerals - these are minerals that are required within the classification of this rock: Feldspar: A petrological term for Feldspar Group. Silica > Quartz: SiO 2: Non-essential minerals - these minerals are common, sometimes major components, but are not always ... gauss elimination method word problem