Radioactive

All Rocks Are Radioactive (and So Are All Bananas), but Meteorites Are Less Radioactive Than Earth Rocks, on Average

Three chemical elements are naturally radioactive occur in all Earth rocks and all meteorites – K (potassium), Th (thorium), and U (uranium). Any rock from any planet will contain at least one atom of these elements so, technically, all rocks are radioactive, it’s just a matter of degree. On average, however, meteorites are considerably less radioactive that typical Earth rocks.


Concentrations of Radioactive Elements in Meteorites, Earth Rocks, Bananas, and People

  Substance K (ppm) Th (ppb) U (ppb)
1 Ordinary Chondrites
(88% of all stony meteorites)
780–825 42–43 12–13
2 Sayh al Uhaymir 169
(the most radioactive meteorite)
4400 31,000 8000
3 Earth’s Continental Crust
(range of 4 estimates)
9000–26,000 3500–7200 900–1800
4 Meteorwrongs
(mean of 598 samples)
10,200 6300 2500
5 Terrestrial Granite
(range of 18 diverse samples)
23,000–57,000 1500–130,000 800–63,000
6 My Kitchen Countertop
(garnetiferous leucogranite)
47,700 16,200 2100
7 A Banana
(a good source of potassium!)
3800 ?, but low ?, but low
8 Human Being 2000–3000 ~1 ~1

ppm = parts-per-million (μg/g), ppb = parts/billion (ng/g)
1. Ordinary Chondrites data from
Wasson J. T. and Kallemeyn G. W. (1988) Compositions of chondrites, Philosophical Transactions of the Royal Society of London A, v. 325, p. 535-544.

2. SaU 169 data from
Gnos E., Hofmann B. A., Al-Kathiri A., Lorenzetti S., Eugster O., Whitehouse M. J., Villa I., Jull A. J. T., Eikenberg J., Spettel B., Krähenbühl U., Franchi I. A., and Greenwood G. C. (2004) Pinpointing the source of a lunar meteorite: Implications for the evolution of the Moon. Science, v. 305, p. 657-659.

Korotev R. L, Zeigler R. A., Jolliff B. L., Irving A. J., and Bunch T. E. (2009) Compositional and lithological diversity among brecciated lunar meteorites of intermediate iron composition. Meteoritics & Planetary Science, v. 44, p. 1287-1322.

Dr. Hofmann told me that SaU 169 did, in fact, register as radioactive with a laboratory survey meter (below).

3. Earth’s Continental Crust data from
Mason B. (1966) Principles of Geochemistry, Third Edition, John Wiley & Sons, New York, pp 329.

Weaver B. L. and Tarney J. (1984) Physics and Chemistry of the Earth (Pollack H. N. and Murthy V. R., eds.), v 15, Pergamon, Oxford, p. 39-68.

Taylor S. R. and McClennan S. M. (1985) The Continental Crust: Its Origin and Evolution, Blackwell Sci. Publ., Oxford, p. 312.

Wedepohl K. H. (1995) Geochimica Cosmomochimica Acta v. 59, p. 1217-1232.

4. Terrestrial Granite data from
Govindaraju K. (1994) 1994 compilation of working values and sample description for 383 geostandards. Geostandards Newsletter, v. 18, p. 1–158.
5. My Kitchen Countertop data from my laboratory
6. Meteorwrongs. I encourage people to obtain a chemical analysis of their rock if they really want to know if it is a meteorite. This row contains average concentrations for 598 rocks for which people have sent me the data and there were data for all 3 elements. Five of the 598 “meteorwrongs” were, in fact,  meteorites – 4 ordinary chondrites and 1 iron.
7. Banana data from https://www.chiquita.com/fruits/bananas-class-extra/
8. Human Being data from several internet sources.

If a rock registers substantially above background on a laboratory survey meter (“Geiger counter”), then it is not a meteorite (but, see SaU 169 above for the only exception of which I am aware).