Granite and feldspar. The term "granitic" means granite-like and is applied to granite and a group of intrusive igneous rocks with similar textures and slight variations in composition and origin. These rocks mainly consist of feldspar, quartz, mica, and amphibole minerals, which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende) peppering the lighter color minerals. Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is known as a granite porphyry. Granitoid is a
Harz granite crystals can be up to 18 mm across. Birkenkopf granite was quarried on the Großer Birkenkopf hill south of Hasselfelde. It is a medium-grained granite with blue-grey coloration. In the quarry 30 to 40% blocks of stone could be used for sawing and 50% of exploitable rock debris could be obtained. The quarry closed in 2009. Birkenkopf granite contains 31.3% quartz, 42.6% alkali feldspar, 20.4% plagioclase feldspar, 5.4% biotite and chlorite as well as 0.3% ore minerals like magnetite, pyrite and hematite. The quarry for Wurmberg granite was situated about 2.5 kilometres north of Braunlage and 250 metres high on