Although granite is a good material of construction, some areas of granite will overflow radon, a natural radioactive gas. Radon causes lung cancer, and 13% of Hong Kong's lung cancer deaths are caused by radon concentrations.
Coarse-grained or medium-grained intrusive rocks, rich in quartz and feldspar, are the most common plutonic in the Earth's crust and are cooled by magma deep in the Earth's crust. Granite is once an important industry because it can be used as paving stones and building stone. Granite can be produced in dikes or rock beds, and more representative of irregular rock mass with great changes in scale. The main components are feldspar, plagioclase and alkaline feldspar are generally rich, the relative abundance of the two become the basis of granite classification.
In most granite, the ratio of two types of feldspar here is less than 1/2. This category has most granite in eastern, central and southwestern United States, southwest England, the Baltic Earth Shield, west and central France, Spain and many other areas. Plagioclase is much more granite than alkaline feldspar, and is common in some parts of the western United States. Much more alkaline feldspar than plagioclase is produced in New England, in many locations in the Oslo Region of England and Norway, but are smaller rocks that are widely developed in the northern part of Nigeria. Less than 20% of the quartz in the rock is not called granite, and the maximum content of dark-colored minerals (iron-magnesium minerals) is about 20% (by volume). The less important minerals in granite are muscovite, biotite, amphibole, or rare iron olivine. Biotite can be produced in any type of granite, and is usually available, albeit at a very low level. Sodium-Containing amphibole and diorite (sodium glitter, sodium iron flash stone, neon stone) are characteristic of alkaline granite. If none of the two types of feldspar is much larger than the other, then amphibole and the other are unlikely to be major minerals, and dark minerals are usually biotite or muscovite, or both.