quartz is the main mineral of granite. the morphology of the granite like except in vermicular and in hypabyssal rocks and lavas were spotted six party crystal double cone, it is shaped granular crystals in most cases. color from colorless to smoky gray. the crystal is shiny glass, but is common to the oil sheen on the surface of fracture. symbiosis with acidic potassium feldspar, plagioclase, biotite. the weathering resistance is strong, and the rock weathering surface often shows obvious uplift. no cleavage is and feldspar difference, can not see the twin, and no oil sheen weathering products.
2, potash feldspar
potassium feldspar includes orthoclase and microcline and perthite, sanidine etc.. produced in the intrusive rocks are mainly of orthoclase and microcline in hypabyssal rocks and lavas can be sanidine. perthite is orthoclase or microcline and albite over the product, which is more than orthoclase or microcline albite. color is an important indicator to identify potash feldspar. potassium feldspar is usually red meat, but there was purple, white, gray, or black. in the course of weathering, the color of potash feldspar will change, and the red color of meat can be turned into grey and white. but also often acid plagioclase was red meat. therefore, the color can not be used as a characteristic marker of potash feldspar. in the plutonic rocks in k-feldspar and microcline are usually anhedral granular crystal. when the potassium feldspar phenocrysts in porphyritic porphyritic rocks, like in form, often with a plate, plate columnar euhedral crystals. field evaluation of feldspar should pay special attention to twin observation. when the rotation were found on the cleavage plane appear half reflecting feldspar, half are not reflective, this is when a white reflective carlsbad twin; is polysynthetic twin. often with potassium feldspar and plagioclase carlsbad twin, often with polysynthetic twin. this is a sign of the difference of potassium feldspar and plagioclase is the most important. if the large k-feldspar crystals, see roots like veins and veinlets, color is shallow, is perthitic. during the weathering of potassium feldspar, the white clay kaolinite is often formed.
3, xie changshi
斜长石广泛出现在各类岩浆岩中。斜长石的种类和含量对于岩浆岩的分类和鉴定至关重要。斜长石可呈不同的色调，一般基性斜长石颜色较深，为深灰色到灰白色；酸性斜长石颜色较浅，可呈灰白、肉红色。基性斜长石由于遭受钠黝帘石化，其蚀变产物常带绿色色调；而酸性斜长石易绢云母化，其风化产物多呈灰白色。在基性浅成岩或喷出岩（如辉绿岩、玄武岩）中，由于斜长石颜色较深且结晶细小，因此很难辩认。这时，可采集半风化的标本观察，由于斜长石风化后颜色变浅，而与暗色矿物易于区别。聚片双晶是斜长石的重要鉴定标志。将标本向不同方向旋转，直到用野外或放大镜看到晶面或解理面上出现一组平行的明暗相间的直线或折线，这就是双晶纹。一般情况下，酸性斜长石双晶纹密集且平直，而基性斜长石的双晶纹较稀且不够平直。 plagioclase widely appear in all kinds of magmatite in. the type and content of plagioclase is crucial for the classification and identification of magmatite. can show different shades of plagioclase, generally the mafic color is deep, dark gray to gray white; acidic plagioclase is lighter in color, gray, red meat. the mafic due to sodium zoisitization, its alteration products often with green color; and easy acid plagioclase sericite, the weathering products mostly white. on the base of rocks or volcanic rocks (such as diabase, xuan wuyan), because the color is deep and fine crystallization of plagioclase, so it is difficult to identify. this observation can be collected semi weathered specimens, due to weathering of plagioclase pale, and can be easily distinguished from dark minerals. polysynthetic twinning is an important sign of plagioclase identification. the specimen with different direction, with the field or a magnifying glass to see a group of parallel dark and straight line or a line or plane appears on the cleavage plane until it is twin. in general, acid plagioclase twin dense and flat, while the mafic twin is thin and not straight.
hornblende is often diorite, syenite in minerals, often appear in granite. hornblende is black, dark green, sometimes brown. amphibole in the intrusive rock in a long columnar crystal, but in some granite, granodiorite, hornblende has elongated crystal habit is not significant. in amphibole cleavage, gloss and hardness and therefore easy to pyroxene similar confusion and pyroxene. the field identification according to the extinction angle distinguish. the specific approach is: to see a group of reflecting good ladder reflector in the light irradiation (cleavage), and then rotate the specimen in the eyes, until the observed second groups reflecting surface, the rotation angle is the angle between the cleavage. if the estimated angle of nearly 90 degrees, which is more obvious for pyroxene; if a sharp angle or obtuse angle for amphibole. in addition, the ordinary stone often associated with hornblende quartz, feldspar, biotite and clinopyroxene and olivine; often, mafic symbiosis. in granite, hornblende and biotite are sometimes confused, the difference lies in the fact that amphibole hardness is greater than a knife, with a knife carved only clastic particles on the cleavage plane of glass luster; while biotite hardness is less than a knife, with a knife can pick into thin slices, cleavage mask pearl luster. in addition, amphibole weathering after often with green shades, and biotite weathering often with brown color.
pyroxene is ultrabasic rocks and basic rocks in the main mineral, also in the andesite often appear as phenocrysts. most of the pyroxene is greenish black and a small amount of pyroxene is greyish green (e.g. tou huishi). pyroxene in intrusive rock is generally equiaxed grain. pyroxene with two groups of vertical cleavage, often constitute a ladder shaped irregular fracture. the most common secondary changes of pyroxene are the petrochemistry and the petrochemistry. serpentine metasomatism often formed with pyroxene silk silk stone "".