Editing Granite (section)

==Natural radiation==
[[File:Fluorite-quarzo-ortoclasio.jpg|thumb|Pegmatitic granite composed of orthoclase and quartz]]
Granite is a natural source of [[Particle radiation|radiation]], like most natural stones. [[Potassium-40]] is a [[radioactive isotope]] of weak emission, and a constituent of [[alkali feldspar]], which in turn is a common component of granitic rocks, more abundant in [[alkali feldspar granite]] and [[syenite]]s. Some granites contain around 10 to 20 [[parts per million]] (ppm) of [[uranium]]. By contrast, more mafic rocks, such as tonalite, [[gabbro]] and [[diorite]], have 1 to 5 ppm uranium, and [[limestone]]s and [[sedimentary]] rocks usually have equally low amounts.

Many large granite plutons are sources for [[palaeochannel]]-hosted or roll front [[uranium ore deposits]], where the uranium washes into the [[sediment]]s from the granite uplands and associated, often highly radioactive pegmatites.

Cellars and basements built into soils over granite can become a trap for [[radon]] gas,<ref>{{Cite web |last=US EPA |first=OAR |date=2015-05-04 |title=Granite Countertops and Radiation |url=https://www.epa.gov/radiation/granite-countertops-and-radiation |access-date=2024-09-12 |website=www.epa.gov |language=en}}</ref> which is formed by the decay of uranium.<ref>{{cite web|url=http://www.world-nuclear.org/images/info/decayseries.gif |title=Decay series of Uranium |access-date=2008-10-19 |url-status=dead |archive-url=https://web.archive.org/web/20120309161714/http://www.world-nuclear.org/images/info/decayseries.gif |archive-date=March 9, 2012 }}</ref> Radon gas poses significant health concerns and is the number two cause of [[lung cancer]] in the US behind smoking.<ref name="cancer1">{{cite web|url=http://www.cancer.gov/cancerTopics/factsheet/Risk/radon|title=Radon and Cancer: Questions and Answers|publisher=National Cancer Institute|access-date=2008-10-19}}</ref>

[[Thorium]] occurs in all granites.<ref name="Hubbert1956">{{cite web |url=http://www.hubbertpeak.com/hubbert/1956/1956.pdf |title=Nuclear Energy and the Fossil Fuels |author=Hubbert, M. King |author-link=M. King Hubbert |publisher=[[Shell Oil Company]]/[[American Petroleum Institute]] |date=June 1956 |access-date=2014-11-10 |url-status=dead |archive-url=https://web.archive.org/web/20080527233843/http://www.hubbertpeak.com/hubbert/1956/1956.pdf |archive-date=2008-05-27}}</ref> [[Conway granite]] has been noted for its relatively high thorium concentration of 56±6 ppm.<ref>{{Cite journal
 | pmid = 16591014
| pmc = 221093
| year = 1962
| last1 = Adams
| first1 = J. A.
| title = The Conway Granite of New Hampshire As a Major Low-Grade Thorium Resource
| journal = Proceedings of the National Academy of Sciences of the United States of America
| volume = 48
| issue = 11
| pages = 1898–905
| last2 = Kline
| first2 = M. C.
| last3 = Richardson
| first3 = K. A.
| last4 = Rogers
| first4 = J. J.
 | doi=10.1073/pnas.48.11.1898
| bibcode = 1962PNAS...48.1898A
| doi-access = free
}}</ref>

There is some concern that some granite sold as countertops or building material may be hazardous to health.<ref>{{cite web |title=Granite Countertops and Radiation |date=4 May 2015 |url=https://www.epa.gov/radiation/granite-countertops-and-radiation |publisher=United States Environmental Protection Agency |access-date=7 January 2020}}</ref> Dan Steck of [[St. John's University (New York City)|St. Johns University]] has stated<ref>{{cite book
 | chapter-url= http://www.aarst.org/proceedings/2009/PRE-AND_POST-MARKET_MEASUREMENTS_OF_GAMMA_RADIATION_AND_RADON_EMANATION_FROM_A_LARGE_SAMPLE_OF_DECORATIVE_GRANITES.pdf
 | title= Nineteenth International Radon Symposium|pages= 28–51|chapter=Pre- and Post-Market Measurements of Gamma Radiation and Radon Emanation from a Large Sample of Decorative Granites | first= Daniel J.
 | last= Steck | year=2009
}}</ref> that approximately 5% of all granite is of concern, with the caveat that only a tiny percentage of the tens of thousands of granite slab types have been tested. Resources from national geological survey organizations are accessible online to assist in assessing the risk factors in granite country and design rules relating, in particular, to preventing accumulation of radon gas in enclosed basements and dwellings.

A study of granite countertops was done (initiated and paid for by the Marble Institute of America) in November 2008 by National Health and Engineering Inc. of USA. In this test, all of the 39 full-size granite slabs that were measured for the study showed radiation levels well below the European Union safety standards (section 4.1.1.1 of the National Health and Engineering study) and radon emission levels well below the average outdoor radon concentrations in the US.<ref>{{Cite web
| archive-url = https://web.archive.org/web/20101103083546/http://www.marble-institute.com/industryresources/countertops_radon_wp.pdf
| archive-date= 3 November 2010
| url = http://www.marble-institute.com/industryresources/countertops_radon_wp.pdf
| url-status= usurped
|title= Natural Stone Countertops and Radon
| author = Environmental Health and Engineering
| year = 2008
|access-date=2023-02-20}}</ref>