Granite forms from sow cooling of a melted rock, which will almost always burn off any coal that's already there when the magma intrudes. Coal deposits from water (usually) buried under things, which is decided a non-melted environment. Note that very rare circumstances can results in coal touching granite, but it would require the presence of an unconformity (that is, the granite would need to be exposed and have coal deposited on top of it).
Granite is indeed an igneous rock; it's what happens as the melt cools slowly to form largish crystals. If the crystalized granite undergoes metamorphic processes, it forms a rock known as gneiss. The fun thing about granite is that its basic constituents (quartz, feldspar, and the other darkish crap left over from the other two) can be polluted in lots of ways to get pretty colors. Red granite, for example, is what happens with a little iron contamination in the feldspar. The about and size of the darkish grains broadly determines its overall darkness.
Granite is an intrusive kind of rock. It forms deep underground where a melt intrudes into an existing body of rock. The granite slowly cools, allowing the crystals to grow moderately large. As the quartz and feldspars crystallize, they force out lots of water and other materials. This hydrothermal (hot water) fluid forces its way out into surrounding rock, further metamorphosing it and depositing a lot of the stuff forced out of the cooling granite block. The heat itself will also distill off volatile fractions of the host rock, including organic materials such as coal. It can also cook off and mobilize relatively volatile rocks such as limestone and gypsum. Limestone gets cooked to marble if it can't get away.
The same material that forms granite can erupt on the surface where it usually forms a rock known as Andesite, a fine-grained and hard grayish rock.
Reply With Quote