Granite is an igneous rock, which means it formed when melted rock solidifies. Granite is defined as having at least 20% quartz and up to 65% alkali feldspar by volume. This feldspar is what often gives granite a characteristic pink colour, although the rock garden specimen is mostly white and grey. Porphyritic means that some of the mineral crystals in the rock are much larger than the surrounding mass of smaller crystals.
A batholith, which is where this rock originated, is a large emplacement of igneous rock, which formed from magma (molten rock) that cooled deep underground. Granite is a common rock type found in batholiths.