A case of secondary growth of primary porphyry field states. One new combination of twin quadruple laws. Twins along the first axis and perpendicular to it

Abstract

In one of the thin sections of quartz porphyry from the Vtoro-Blagodatny mine, I came across an interesting case of cracks in feldspar grains being filled with feldspathic substance of the same composition and in the same orientation. The rock is quite strongly altered: feldspars are abundantly strewn with muscovite dust. The thin section field is cut by several veins, apparently made of new growths. Moreover, depending on whether the vein cuts through the ground mass or feldspathic segregations, it is made either by an aggregate of feldspars and quartz or only by feldspars, with such a slight difference in orientation with the mineral of the grain cut through by the vein that it cannot be quantified. Feldspar veins are characterized by significantly greater transparency due to the absence of muscovite inclusions.