Granite Thin Section

The mineralogy of this granite is relatively simple biotite quartz and two feldspars plagioclase and k feldspar.

Granite thin section. These are photographs of a thin section of granite magnification 10x perhaps the most common igneous rock we encounter. Almost colorless to neutral. Outcrops of granite tend to form tors domes or bornhardts and rounded massifs.

S type granites can also contain aluminium rich iron and magnesium rich biotites. These are photomicrographs very thin slices of rock seen in plane polarised light or between crossed polarisers when the colours seen are produced by interference of light. Biotite metaluminous granite showing a close up of one crystal.

Fluorapatite ilmenite and titanite are also present in minor amounts. Hornblende and biotite are the commonest mafic minerals however muscovite is also frequently encountered. Very high positive habit form.

Much of it was intruded during the precambrian age. Pyroxene andalusite corundum tourmaline. Euhedral to subhedral grains with a wedge or diamond shaped cross section are common as are rounded or irregular anhedral grains.

This means that biotite in standard thin sections rarely goes completely extinct. Sign in to download full size image figure 4 12. Granite is a medium tocoarse grained acid igneous rock with essential quartz 20 and feldspar where alkali feldspar constitutes between 100 and 35 of the feldspars and minor mafic minerals.

Photomicrographs of these minerals in thin section from s type granites of the lachlan fold belt are shown in figure 2a and 2b. The large pink carlsbad twinned k feldspar megacrysts dominate the thin section. Granite containing rock is widely distributed throughout the continental crust.