Scientists want to use a mineral to detect nuclear exposure in space

Turns out, the mineral not only changes color upon nuclear exposure- its structure changes too.
Sade Agard

According to a recent study published in the Materials Horizon journal in September, researchers have just discovered a unique and novel intelligence property of hackmanite called gamma exposure memory. The finding could allow hackmanite as a radiation detector- including applications in space.

Plans for a UV radiation detector to be tested aboard the International Space Station

Hackmanite is a rare natural mineral that has been the subject of much research at the University of Turku in Finland. Now, a research group at the institution has discovered a way to synthesize hackmanite and use its brightness and color-changing capabilities to develop several detection applications.

The team is currently working on a non-electronic, hackmanite-based UV radiation dosimeter that will be tested aboard the International Space Station. By observing hackmanite's transformation from white to pink due to UV rays, radiation exposure in space can be calculated.

The scientists, along with laboratories of Swedish partners, the Finnish Radiation and Nuclear Safety Authority, and the radiochemistry laboratory of the University of Turku, looked at the reactions of the synthetic hackmanite to beta particles (positrons), gamma radiation, and alpha particles. They found that hackmanite exhibits color changes in response to various radiation types, indicating that it is a 'radiochromic' substance- a previously unknown property.

Nuclear radiation creates an unexplored structural defect in hackmanite

But that wasn't all. The key to discovering the new feature was when the researchers could verify, with computational results, that nuclear radiation creates a new type of structural defect in hackmanite. This defect functions as a specific kind of memory device for the material.

While hackmanite is not destroyed by radiation, it does provide a novel kind of intelligent function (i.e., gamma exposure memory), which has not been found in any other substance, according to the researchers.

Despite the gamma exposure memory and the structural defect, hackmanite maintains one of its core intellectual properties—the ability to alter its color continually.

The memory trace will remain even when the color is changed back to the original

Professor Mika Lastusaairi, leader of the research group, in a statement further explains, "the memory trace will remain even when the color is changed back to the original. It becomes visible when the sample is colored again using a UV lamp."

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"To the naked eye, the color is similar to the material exposed to UV radiation or X-rays, but spectrometry reveals a small but distinct change in the shape of the signal," Lastusaairi continues.

Current and future uses of hackmanite in the nuclear radiation industry

Hackmanite can make radiochromic films, frequently employed in various medical physics applications to quantify radiation doses. The mineral can map dose distribution- thanks to its ability to change color when exposed to nuclear radiation.

According to the study, Hackmanites are non-toxic, and films made of the material are reusable. Most modern radiochromic films are made of leucomalachite green or polydiacetylenes and are either poisonous or non-reusable. Therefore, hackmanites show great potential to replace the currently available radiochromic films.

The discovery of hackmanite's memory quality- a property those other substances do not have-makes the material a cheap, quickly produced, and environmentally friendly alternative.


Radiochromic films are used as position-sensitive dose meters in e.g. medical physics and radiation processing. The currently available films like those based on lithium-10,12-pentacosdiynoate or leucomalachite green are either toxic or non-reusable, or both. There is thus a great need for a sustainable solution for radiochromic detection. In the present work, we present a suitable candidate: hackmanite with the general formula Na8Al6Si6O24(Cl,S)2. This material is known as a natural intelligent material capable of changing color when exposed to ultraviolet radiation or X-rays. Here, we show for the first time that hackmanites are also radiochromic when exposed to alpha particles, beta particles (positrons) or gamma radiation. Combining experimental and computational data we elucidate the mechanism of gamma-induced radiochromism in hackmanites. We show that hackmanites can be used for gamma dose mapping in high dose applications as well as a memory material that has the one-of-a-kind ability to remember earlier gamma exposure. In addition to satisfying the requirements of sustainability, hackmanites are non-toxic and the films made of hackmanite are reusable thus showing great potential to replace the currently available radiochromic films.

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