stone radioactivity
 
Stone radioactive standards introduced in 2000 --- "《radioactive materials, health protection standards》, according to the intensity of radioactive radiation of building materials will be divided into three levels (categories):

A type of decoration materials: decoration materials in the natural radionuclide radium-226, thorium-232, potassium-40 activity at the same time meet the IRa ≤ 1.0 and Ir ≤ 1.3 requirements for Class A decoration materials. A-class decoration materials production and marketing and the use of unrestricted.Belong to A materail granite :some is :Flower pearl granite ,China peacock green granite ,Luoyuan red granite ,chrysanthemum  yellow granite ,Xili red granite and so on .

Class B decoration materials: Class A decoration material requirements are not met but at the same time meet the IRa ≤ 1.3 and Ir ≤ 1.9 Requirements for Class B decoration materials. Class B decoration materials can not be used for Class I civil interior surface, but can be used for Class I civil construction of the external finishes and all other buildings inside and outside finishes. That is a Class B stone can not be used in buildings such as housing, factories, public living rooms, etc.), but can be used for structures (such as walls, gatehouse, Pavilion, Pavilion, verandas, arch, patio, water towers, chimneys, poles, dams, roads, store, warehouse, etc.);Belong to B materail granite :some are  :Shidao red granite ,Maple red granite ,African red granite ,Taishang red granite and so on .

C-class decoration materials: does not meet A, B class decoration materials but fulfills the requirements Ir ≤ 2.8 for the C-class decoration materials. Class C decoration materials can be used only outside the building walls and other outdoor uses, must limit its sales, which means that the C-class stone can only outdoor The Ir> 2.8 stone to be used only for the roadbed, culverts, dams seawall and deeply buried pipeline project and other places away from people's lives.

In general, the dark stone of radiation higher than the light-colored ,radioactivity of the red stone is the highest, followed by green, pink, gray, black, white; igneous (magmatic rock) higher than the Code metamorphic and sedimentary rocks granite higher than marble, followed by limestone, slate, sandstone.
 
Note: The standard provisions of the International Journal of Radiation Defence Committee (ICRP) radiation radon concentration is less than or equal to 100Bq/m3 of radioactive materials for Health Protection Standard requirements: Class A is not higher than 70Bq; class B is not high The in 90Bq; C higher than 100Bq.