I'm trying to remember the name of a (children's?) sci-fi novel I read as a child in the 1980s.
It was about tiny coloured gemstones that fell from the sky all over a city. Two/three young friends collected some up, then discovered the gemstones were intelligent. The gemstones would connect together to form different shapes and spell out words. One of the friends, I think, formed some sort of mental connection with the stones and could manipulate them.
Although I read it in the mid-80s it might have been written in the 1970s or earlier.
Have searched for it online but can't find anything that fits my recollection. I'm starting to think I imagined it! Any info I'd be really grateful!