If you read the original paper (https://www.frontiersin.org/journals/psychology/articles/10....) then they go into more detail on the piles of pebbles and what got taken; the graphs in figure 4 (https://www.frontiersin.org/journals/psychology/articles/10....) make it very obvious that the chimps loved the crystals.

(an "euhedral" crystal is one with lots of obvious facets, an "anhedral" one is one that's been rounded down into a more pebble shape.)

You have a question, a hypothesis and designed an experiment to test it.

The study had a harder question: "What properties of crystalline stones attracted them?". The abstract has this answer: "We found that transparency and geometric shape were the two attractors guiding chimpanzees."

Maybe this is scientific proof for the diamond industry.

> I’m willing to bet they will go after the smooth rocks and it’s about rarity, not crystals.

Why? Crystals are pretty, rocks are not. We clearly prefer shiny colorful things to dull beige things, even if shiny things are abundant.

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