On July 16, 1945, the United States became the first country to successfully detonate an atomic weapon, signalling the beginning of a new era in warfare and in politics. This detonation took place in the middle of the New Mexico desert, with the bomb placed carefully atop a 100 foot tower. The bomb, nicknamed “Gadget”, had a yield equivalent to 20,000 tons of TNT. Just 24 days later, a functionally similar bomb (using Plutonium, unlike the Uranium bomb at Hiroshima) was dropped on Nagasaki.

No one was completely sure what would happen when Gadget went off. For a while, there was worry that the chain reaction would be unstoppable and react with the entire atmosphere. Before the test, Enrico Fermi took bets from some of the physicists and high ranking military personnel on whether the bomb would destroy the whole state of New Mexico, or the entire planet. The math seemed to show fairly conclusively that the world wouldn’t be destroyed, but a lot of the guards who didn’t know that became anxious. Kenneth Bainbridge, director of the Trinity Project, was not amused with Fermi scaring all the guards.

When the bomb was detonated, it left a crater of radioactive glass in the desert that was 10 feet deep and 1100 feet wide. About 240 people on the project directly watching the blast reported the early morning dawn being lit up brighter than full daylight for one to two seconds and felt a wave of heat roll over them that was “as hot as an oven”, even at a distance of 10 miles away. The shock wave took 40 seconds to propagate to the observers and was felt up to 100 miles away. The enormous mushroom cloud was 7.5 miles high. It was at this point that Bainbridge remarked to Oppenheimer, “Now we are all sons of bitches.” Oppenheimer later spoke his famous line, “Now I am become Death, the destroyer of worlds”, a quote from the Bhagavad Gita.

This famous picture was taken 16 milliseconds after the Trinity bomb exploded. Trinity_Test_Fireball_16msTrinity_crater_(annotated)_2 Trinity-ground-zero-men-in-crater That’s the hypocenter of the blast. Once the public found out about the bomb and where it was detonated (sometime during the late 40’s), they began traveling to the site and collecting the glass as souvenirs for themselves and to sell to tourists and collectors. This area was still lightly radioactive, and the government didn’t like the fact that people were carting off lots of the stuff or sniffing around their test sites. In 1953, the government bulldozed the site, burying any glass that was left and fenced off the area. A law was passed making it illegal to collect samples from the area. The only exception was that it was legal to buy and sell the glass that had already been collected and was already on the market. People began calling the collectible glass “Trinitite”.

The Artifact

You can still buy Trinitite today, on places like eBay or from mineral collectors. You can also buy it from United Nuclear, which is where I got my sample. United Nuclear makes two claims that I wanted to verify: that the sample was real and that the radiation level was safe. Apparently lots of people sell fake Trinitite, because it’s easy to fake and people will buy it. United Nuclear says that they check all the Trinitite they buy with a mass spectrometer to verify authenticity. Here’s what my sample looks like: 2013-02-21 20.32.05 As an undergrad at Georgia Tech, I have access to some unique resources. One of my friends happens to be studying Nuclear and Radiological Engineering, so I asked him if he could measure my sample with a Geiger counter to make sure I wouldn’t get cancer or to confirm that I would get super powers with this thing sitting in my room. He grinned and said, “Oh, we can do better than that.”

The Experiment

After talking to his professor, he got permission to run a bunch of tests on my sample for his lab class. It turns out that a Geiger counter wouldn’t be able to tell me very much about the sample, including how dangerous it really was. Instead, a high purity Germanium (HPGe) detector was used. HPGe detectors are large, expensive machines that must be cooled with liquid nitrogen. Here’s a cross section of a commercially available detector:

“Coldfinger” is also the name of the villain in the next James Bond movie.

Because the detector is so cold, electrons have a lower probability of escaping, which allows for a higher resolution and higher efficiency. The reason Germanium is used is because of its useful properties as a semiconductor. As incoming radiation hits the Germanium, it creates free electrons and holes. An electric field across the Germanium causes all of the electrons to get pushed to one side, creating a current. This current is proportional to the number of holes created, which is proportional to the energy of the incoming radiation. This current is read with a Multiple Channel Analyzer (MCA) that bins the energy from the detector into multiple channels. The efficiency of an MCA changes based on the energy range, so they must be calibrated with known radiation sources before use. To determine if my sample was really from the Trinity test, its activity can be compared to the activity of specific radionuclides measured from glass collected at several other test sites. Gamma spectroscopy can be used to produce a plot that’s a little easier to visualize. To perform the experiment, the MCA was set at 4096 channels with a live time of 120 seconds and calibrated. The sample was placed in the shield surrounding the detector and measurements were taken for 80,000 seconds (22 hours). The sample was then removed and a background measurement was taken for 80,000 seconds.


Here are the results, along with data from other test sites (as of 2013): table Note that percent error here is not standard deviation, it’s how much the measured sample deviates from a known sample. Here is the measured spectrum: spec2 Analysis

The interesting peaks here are Cs-137 at 661.5 keV, Am-241 at 59.4 keV, and K-40 at 1400 keV. The specific activity of Co-60 is very low, which is the biggest clue that the glass was collected from Trinity, rather than another location. For example, at Reggane, Co-60 is 207.2301 Bq/kg as of 2013, while Trinity is closer to 7.771128 Bq/kg. The activity we see here is 1.0 ± 1.0 Bq/kg, which suggests that my sample from United Nuclear is real and came from Trinity! The other thing this data lets us do is see how dangerous the radiation from my sample is. To do this, we simply sum up the counts collected at every energy and divide by the amount of time the sample was measured to get an energy indiscriminate counts per minute. It turns out my sample has a total gamma activity of 1183.29 CPM ± 5.43 CPM. So how do we know if that’s dangerous? That’s a little difficult to answer, because CPM is relative. The type and energy of the radiation matters enormously. This analysis only looked at gamma radiation, since that’s the kind of radiation that is extremely penetrating and difficult to shield. However, gamma radiation is not as damaging as other forms of radiation of the same energy, like neutron radiation. My sample also emits alpha and beta particles, but they are very short range and are easy to block. Alpha radiation can’t penetrate your clothes and beta radiation can be stopped with only a few millimeters of aluminum. So, ignoring alpha and beta radiation, the damage gamma radiation does increases with energy, and we have a wide range of energies in this sample. If we assume all the gamma rays are 661.5 keV from the Cs-137 and you are 1 cm from the source:


The attenuation of photons in water (which closely approximates human tissue) is: eq2 Multiplying those two numbers gives 5.49*10^-13 Gray/second, or 1.73*10^-5 Gray/year. The conversion factor from Grays to Sieverts is 1:1 for photons. 100 Rem is a Sievert. This means that if you keep this sample 1 cm away from you for the rest of your life you will receive 1.73 milliRem per year.

To put that in perspective, the annual background dose is about 2.2 mSv, or 220 mRem. The extra dose you would receive from the Trinitite is about 2 orders of magnitude less than the background dose. In fact, the total dose you receive from sleeping next to someone for 8 hours every night for a year is about 2 mrem, so I would get the same exposure if I cuddled up with a person OR a vial of radioactive glass every night. In other words, it’s safe to store my sample on the shelf in my room.
But what about the other energy levels, like that thing up near 1500 keV? If you do the math, you’ll find that it gives you a much higher dose than the Cs-137, even though it has a lower count. Well, that thing at 1500 keV is K-40, which undergoes beta decay, and that radiation is blocked by the container the sample is in. The reason the radiation dose calculation was done with Cs-137 is because it’s the highest energy isotope that undergoes gamma decay, which is difficult to shield. The reason we see such a large spike of K-40 is because it is one of the largest natural sources of radiation, found in dirt and food and humans. There are lots of really confusing units for dealing with radiation, but one of my favorite units is the Banana Equivalent Dose, which is a measure of the radiation dose (emitted mostly by K-40) that you are exposed to from eating one banana.
If you're lonely, you can eat 200 bananas to get the same effect as sleeping next to someone.

If you’re lonely, you can eat 200 bananas to get the same (radiation) effects as sleeping next to someone.

Now, there is one instance where my sample would be dangerous to your health. Unlike a banana, if you were crazy enough to eat some Trinitite, your risk of cancer would go way up. One of the biggest reasons for that is because the isotopes that undergo alpha and beta decay would now be directly interacting with your tissues. That can be really bad. For example, one of the biggest risks would be Strontium-90, which emits beta radiation. The nickname for Strontium-90 is “bone seeker”, because it behaves biochemically similar to calcium, so almost all of it that remains in your body deposits into your bones and will give you bone cancer.

Bonus Points

There’s one more really neat piece of information we can pry out of the data. A naturally occurring isotope in soil is Eu-151. When Eu-151 captures a neutron from, say, a nuclear explosion, it turns into Eu-152. That’s a great way to estimate the neutron fluence (which is neutron flux integrated over time). So, if we can estimate the neutron fluence of my sample, and since we know how neutrons are emitted by the explosion at different distances, we can estimate how far away from ground zero my sample came from.

The math gets a little hairy here, so get ready.

Eu-151 undergoes an (n,γ) to make Eu-152 (it captures a neutron). The specific activity of Eu-152 is given by this equation:


Where φth is the thermal neutron fluence rate (n cm-2 s-1), a is the isotopic abundance of Eu-151, NA is Avogadro’s constant, M is the atomic mass of europium, c is the Eu concentration in the soil, σth is the thermal microscopic cross section of the (n,γ) reaction, CR is the cadmium ratio for a nuclear reactor, and T1/2 is the half-life of Eu-152. From [3], σth = 5300 barns, CR = 43, and c = 1.2 ppm. The cadmium ratio approximately accounts for the contribution of fast neutrons to the production of Eu-152.

After calculating the flux, one can solve for the distance from ground zero via this equation:


The specific activity of the Eu-152 was calculated by dividing the net counts by the duration of time over which it was counted, the mass of the sample, the efficiency for the energy of interest, and the branching ratio for the decay mode of interest.


After decay correcting the specific activity to the time of the explosion (68 years) and solving for the flux:


Solving for the distance from the center of the explosion:


Solving for the distance from ground zero:


So my sample was collected about 76 meters from ground zero. That means it came from somewhere along this circumference:


Future Work

Some kinds of Trinitite formed from sand on the ground turning to glass, and other kinds formed from sand being drawn up into the explosion, turning to glass, and then raining back down. If my sample was formed on the ground, we would expect the distribution of radionuclides would have an approximately continuous gradient. If it formed in the air, there would be a discontinuity in the distribution. This could be estimated with beta spectroscopy on each side of a sample. If the activity is spatially uniform, then the radionuclides are uniformly distributed. For this experiment, only gamma spectroscopy on one side was performed, so it’s unclear how my sample formed. However, a lot of the pieces in my sample appear large and flat, like they flaked off of the surface of the desert, so I would hypothesize that it formed on the ground. I would expect them to be rounder if they formed in the air.


It’s interesting to think of all the time and effort and money that went in to making the device that created Trinitite. It’s like I have a little vial of second order creations by Fermi and Feynman and Oppenheimer. I learned a lot about radiation physics and now I have a nice test radiation source for other projects that is pretty well characterized.


None of this would be possible without Nicholas Piper, who collected the data, performed analysis, and answered my questions. Also, thank you to his lab partners, Catherine Bartgis, Akshat Bhatnagar, and Benjamin Bane.

1. Tsoulfanidis, Nicholas, and Sheldon Landsberger. Measurement and Detection of Radiation. 3rd ed. Boca Raton, FL: Taylor and Francis Group, 2011. 384-385. Print.

2. Belloni F, Himbert J, Marzocchi O, Romanello V. “Investigating incorporation and distribution of radionuclides in trinitite.” May 5, 2011. Journal of Environmental Radioactivity, 2011.

3. Parekh P, Semkow T, Torres M, Haines D, Cooper J, Rosenberg P, Kitto M. “Radioactivity in Trinitite six decades later.” Wadsworth Center. University at Albany. Journal of Environmental Radioactivity, 2005.

Other interesting Trinity videos


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  2. What is the value of a piece of steel that was severely deformed by the first A-bomb test? Roughly 18″ long & 2 pounds. Is it legal to own? Is it legal to sell? It seems that several if not many ae selling Trinite. Probably from a nearby tower; not the tower that the A-bomb was mounted on? It was picked up on an employee tour before such people were told not to pick up souvenirs. Most picked up several pound of Trinitite.

    • I’m not the guy to appraise it’s value, but of course it’s worth whatever someone will pay for it. Steel shrapnel could have either come from the bomb casing itself or the tower. There was much more steel in the tower, so it’s more likely that it came from there. I’m not a lawyer, so I don’t know for sure if it’s legal to own, but given that it’s legal to own Trinitite that was gathered before the area was protected, I would guess it’s legal to own a piece of metal. If you do want to sell it, you’ll need some kind of proof of authenticity. The best way to do that would be to repeat my experiment and show that the correct isotope ratios exist which could only have come from the Trinity site.

  3. I once read that there were traces of plutonium in trinitite, but yesterday found an analysis that showed U-238. What makes it green?
    I have a sample i got from my dad. I know its the real deal, he lived in Alamogordo and was a Lt. Colonel in the AF.
    Im going to break off a sample, and one I start my studies towards Biology in the Fall…during my Chem classes, I want to try and get someone interested to perhaps analyze my sample in the lab.

    • I think the green color is actually from the makeup of the sand that formed the glass, not an radioactive isotopes. In this case, it’s probably the result of small amounts of iron oxide in the sand. Although you are correct, Uranium glass also looks green, I don’t think there’s enough Uranium in Trinitite to make it look green. If you can find someone at your school who does nuclear and radiological science or engineering, they’ll have better equipment for analyzing your sample than the chemistry department probably will. Good luck with your analysis!

    • Maybe a bit late but some people might still be interested in this.
      The green color in the glass actually doesn’t come from Uranium isotopes, nor Plutonium isotopes. It comes from iron ions that were melted into the glass. A little bit from the ground and most from the tower and Trinity case/components. Also, Uranium metals and Plutonium metals are grey-ish like iron. The green color associated with radioactive elements and actually comes from the luminescence of the first Radium dials etc. No radioactive element is green, nor do they glow green. Actually, no element glows on it’s own because of ionizing radiation. Besides one of course, Actinium, a element so radioactive that it ionizes enough air around it, to produce a pale blue glow. There is also Cherenkov radiation, which is also blue. And last but not least, Natural Uranium minerals are mostly red or black, with the exception of a few ones, which are green because of copper oxides.

  4. Brad Jones

    Hi, I read your article and about 99% of it was well above my level of understanding (and admittedly I have a short’ish span of attention so I skipped much of the parts that looked scary). I was looking for the part that said either “yes” or “no” the sample was genuine. I didn’t see it. Im guessing that you concluded that it was real (to the best of your ability), but I didn’t see that conclusion written.

    • Yes, I was able to conclude that the sample was real based on the fingerprint of isotopes we found in it. There are other publications that have shown the fingerprints of known detonation sites around the world, and comparing mine to the Trinity site yields an almost exact match. The beginning of the Analysis section is where I talked about that.

  5. What a great article! Thanks for taking the time to write it up! I didn’t realize there are lots of fakes of trinitite around the internet. The brief search I did had unverified samples that were twice as expensive as from united nuclear. I know where to get a sample from now.


  6. Sorry, I don’t completely understand the table.
    “Note that percent error here is not standard deviation, it’s how much the measured sample deviates from a known sample. Here is the measured spectrum”

    The deviations appear to be 80 -97 %. What is the known sample and what about these deviations? Counter-intuitive to me.; what shows your samples are real?
    Thanks, RR

    • Good question. That table is showing how far off the measurements of each radionuclide in the Trinitite sample were from data collected in other studies where the sample was known to be good. The known good data came from here:
      1. Tsoulfanidis, Nicholas, and Sheldon Lands-berger. Measurement and Detection of Radiation. 3rd ed. Boca Raton, FL: Taylor and Francis Group, 2011. 384-385. Print.

      2. Belloni F, Himbert J, Marzocchi O, Romanello V. ”Investigating incorporation and distribution of radionuclides in trinitite.” May 5, 2011.
      Journal of Environmental Radioactivity, 2011.

      3. Parekh P, Semkow T, Torres M, Haines D, Cooper J, Rosenberg P, Kitto M. ”Radioactivity in Trinitite six decades later.” Wadsworth Center.
      University at Albany. Journal of Environmental Radioactivity, 2005.

      The errors all seem quite high which is due to the fact that the reference samples came from different distances from the explosions which fused sands of different kinds of rocks, and each explosion took place at a different time, so the decay products were different. I provided that table for completeness, but it’s easier to interpret the results if you look at the table above it, which shows that Co-60 at Trinity had an activity of 7.8 Bq/kg, and the sample tested here had an activity of 1 Bq/kg, whereas the Reggane site had 207 Bq/kg. You could say that the measured activity of Am-241 is a better match for the Semipalatinsk site, but the Co-60 and Cs-137 activities are so far off, that we can rule that out. Now, we didn’t test a sample from every single atomic explosion site (it’s unlikely that anyone could as there have been almost 2500 separate nuclear explosions in the world). So it is in theory possible that this sample is from a DIFFERENT explosion, however the data we collected shows that 1) it DEFINITELY came from some kind of atomic bomb and 2) it happens to match quite closely to other samples taken from the Trinity site. I think it would be unlikely that United Nuclear either measured a bunch of “Trinitite” from different explosions to find one that matched the activity profile of Trinitite or that they just got that lucky. Real Trinitite isn’t that scarce, people collected tons of it back when it was legal.

      • What confuses me is you state the activity of Co-60 from the known Trinity site is 7.8Bq/kg while that from your claimed Trinity sample is 1Bq/kg. IF they both are from the Trinity site, as is claimed, shouldn’t they have the same activities?
        Even if the sample was collected about 76 meters from ground zero I do not understand the somewhat large differences in activites. 76 meters is not all that far when dealing with the huge energies generated by nuclear fission. Now if it were 76 Miles, that would be a completely different story. What happened? IDK!

        • They won’t have exactly the same activity because the distribution of radionuclides isn’t perfect. There are a tone of different units to describe how radioactive something is and it can get really confusing, but a Becquerel is one decay per second. So the difference between one decay per second per kilogram and 8 decays per second per kilogram isn’t enormous. It is different, and I’m not a nuclear physicist so I could be wrong, but it seems quite close given that we don’t know exactly where my sample and the reference sample were collected from.

  7. Thank you for taking time to write up your Trinitite research in detail. I believe the first equation under Bonus Points for specific activity has a lower-case “t” in the numerator that isn’t defined or needed. In a paper by Semkow on Modeling the Effects of the Trinity Test, an exponential term appears with the cadmium ratio to account for self-shielding. In order to neglect this term, I think you must have assumed it was less than 0.00001. Was there any basis for this? Regarding fake Trinitite, I have yet to find any and I’m doubtful of claims that any significant amount has been sold.

  8. Hey there, don’t know if this site is still active or I’m talking to dead space, but I began a crystal, gem mineral business about 18 months ago, and just won an auction on ebay for a lot filled with gem and mineral specimens from over 60-70 years, and included was a few pieces of trinitite with the history included handwritten. We used a small Geiger counter and it didn’t really register. So since I don’t understand all your technical stuff in this awesomely done report, should I handle the pieces or not? 🙂
    Thanks so much for your help. The dealer I bought it from is 86 years old and I hate to bother him.
    Sheri Lawson

    • Trinitite is safe to handle, but the main danger is the dust is creates. You will definitely want to avoid breathing in anything or accidentally ingesting any particles if they get on your fingers and then you eat something. Depending on where your sample came from, it could have different isotopes in it. I can’t say for sure how dangerous your sample is, but I would mostly be careful to keep any from getting inside me. Even alpha radiation, which is normally harmless to you, can cause a lot of damage once it gets inside your body, as your soft tissues directly absorb it. The best thing to do would probably be to put it in a glass jar or vial. That way you can keep track of it and prevent people from handling it and forgetting to wash their hands afterwards. Again, I can’t know for sure what your sample is or how dangerous it is, but if it’s really run-of-the-mill Trinitite, that’s a safe way to contain it.

  9. Very interesting article and a good read. I regularly scour the web for new papers or articles about it, but somehow missed this one until recently.

    I collect and sell trinitite (meteorites also), and I have samples in my collection that I would be willing to donate to the author for the purposes of study. I have had pieces with anomalous characteristics, and my material has been authenticated by reputable scientists. What I do not know, us exactly how far from Ground Zero my pieced originate from, and at what height any pieces may have formed while airborne. Feel free to contact me via email. I have test results and relevant academic material I can share. 🙂

    Best regards,


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  11. I have a quite large piece of glass that my grandfather brought home from the bomb of Hiroshima. He has passed away and I never got to ask. But why does it turn colors?

    • That’s probably a result of the type of rock/media itself, not anything to do with the nuclear blast that formed it. What’s happening is the crystalline structure of the rock diffracts light differently depending on how the incoming light hits it. Opals are one of the best known examples of this.

  12. Very interesting article since the government thinks its safe to work there. In 1983 I worked on the trinity site for a year between 1 and 4 KM from ground Zero. There is still lots of this material everywhere around the site. If you could please email I have several questions I would like to ask.

  13. I have a large collection of Trinitite and it is not a danger any more as the trace of cesium 137 is so low at this point in time it has lost its POW. I am selling this collection with certificates of authenticity. 5053196448

  14. Aaron Kemper

    If I get my Trinite of United Nuclear and if I let it sit in there and not touch it or anything will it still give off radiation ?

    • Yes, radioactive materials always give off ionizing radiation regardless of if they’re handled or not. The alpha radiation it gives off will be stopped by the glass vial, but the beta and gamma radiation will make it out into the room. However, as the analysis showed, it’s not dangerous to humans unless you eat the Trinitite (ASSUMING your sample came from the same place mine did).

  15. Hi Hunter, Thank you for this article! I have referenced it several times. I have amassed a large amount of Trinitite that was collected by Dr. Ralph Pray and am now selling it online. I receive a lot of questions regarding the levels of radiation and your article has been invaluable. Thank you again! Scott – http://www.atomicrockshop.com

  16. David Wargowski

    This was a fantastic article. Great analysis work that demonstrated how complex radiation measurement is. Its not just about running around with a Geiger counter that most people have come to believe due to mis-information, lack of information, and/or lack of understanding. You were very fortunate to have such resources at your disposal.

  17. Do you know if there is any plutonium at all potentially in a sample of trinitite?

    • I highly doubt it. Plutonium would have been the limiting reagent in the detonation, and while one of the products of a plutonium based nuclear explosion is Plutonium 243, it only has a half life of 5 hours.

  18. I disagree about trinitite not containing plutonium. The Trinity device was not that efficient, and only about 15% of the plutonium in the core fissioned. In addition, the bomb had a natural uranium (99.3% U238) tamper, and a significant percentage of the uranium 238 in the tamper would have been transmuted into plutonium 239 by the neutron bombardment during the explosion.
    I doubt that the amount of plutonium in the trinitite is very large, most likely in the low ppm levels, since most of the plutonium that escaped in the blast presumably drifted away in the mushroom cloud as fallout. It is a reasonable assumption that less than one part in 100 of the plutonium got into the glass layer on the soil surface. Logically, though, there must be some present.

  19. Would you be interested in analyzing a piece from Hiroshima? My mother collected–illegally, might I add–the melted glass when she and my father visited the site sometime in 1950, while they were stationed in Japan during the occupation. After my mother passed away, I found it in a small cedar box amongst her things. My father had to explain what it was since they never spoke about it. I’ve been wondering about it’s radioactivity level.

    • That sounds really interesting, but I don’t have access to the equipment that I used to perform this analysis anymore. You might want to try contacting a college or university that has a nuclear engineering program and see if they will look at it.

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