Give a chimpanzee a crystal and you might not get it back. So say the researchers who recently offered quartz, calcite, and other crystals to chimps at a primate rehabilitation center near Madrid, Spain. They were trying to understand why humans love crystals, so they gave the shiny minerals to chimps, one of our closest animal relatives. And the apes went wild. They stared at a large crystal on a pedestal before snatching it away, and they carried other crystals into their living quarters and never brought them back. Researchers had to trade many bananas and yogurt for one. Discoveries at archaeological sites suggest that prehistoric predecessors of humans gathered crystals as far back as 700,000 years ago. Today they’re popular as jewelry or trinkets, often believed to have supernatural properties. The researchers proposed that chimps are attracted by the transparency and shape of crystals, which sets them apart from the rest of the natural landscape. That’s likely why prehistoric humans were interested as well. Study author Juan Manuel García-Ruiz told IFLScience, “If our results are correct, then we have had crystals on our minds for at least 7 million years.”