What sounds like a science fiction plot is reality for Australian researchers, who are anxiously waiting for the precious cargo to arrive from Shanghai.
The crystals, which have taken more than a decade to produce, will be at the heart of a world-leading project to detect dark matter particles in the depths of a mine shaft in Stawell, western Victoria.
Dark matter is a highly elusive, invisible material thought to make up about 80 per cent of the universe and hold galaxies together.
A team of physicists has been working in a lab one kilometre underground at the Stawell Gold Mine, building on international research to detect dark matter.
The highly-purified crystals will be installed in the lab and are expected to flash with a burst of light when they interact with dark matter particles.
"This has taken a lot of research and development because this is the most pure sodium iodide crystal ever made," University of Melbourne physicist and project director Elisabetta Barberio told AAP.
But before the experiment can commence, the crystals have to survive the fraught weeks-long sea journey from China.
"As soon as there's a little bit of humidity, they melt," Professor Barberio said of the crystals.
It's been a long road to both grow and transport them.
American scientists began producing the powder to make the crystals about a decade ago, far from agricultural zones where potassium in the air from fertiliser could contaminate it.
The crystals were then grown in a lab in Shanghai, carefully kept sterile and dry for years.
They have been packed in a dark, dry, vacuum-sealed and padded box to come to Melbourne, where they will be collected and driven to Stawell.
Once at the mine, the box will be carefully monitored by an accelerometer to minimise vibration while it is slowly lowered into the underground lab.
Scientists will decontaminate the box before opening it and store it in a nitrogen-filled tank to keep it pure and dry, before installing the crystals into the detector.
Prof Barberio said the extreme measures would keep the crystals safe from radioactivity.
"Dark matter interacts very, very rarely, like maybe a couple of times a day," she said.
"But if you have radioactivity around you, radioactivity like a neutron can mimic dark matter ... and there will be a lot of false positives."
Even when the crystals are in place, the physicists are not certain they will see anything at all.
But that's the nature of science, Prof Barberio said.
"If we see something, that's huge," she said.
"But if we don't see anything, we can rule out a lot of hypotheses.
"It's a little bit like being an investigator."
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