The Calx are a Silicon based life form. Looking like nothing so much as large glassy rocks, the entire race is naturally telekinetic. This explains how they’ve achieved so much technologically in spite of the fact that they don’t actually have any hands. They can communicate by vibrating themselves to produce sound.
An average Calx vaguely resembles a 2 meter tall broad based irregular cylinder diagonally bisected. Their coloration varies greatly, and many members have veins and striations of different colors.
It is assumed they originate on a much warmer world than Earth, possibly more similar to Mercury, but not much else is known of them.
They seem to have cordial relations with most races, which makes sense. After all, who wants to fight with a giant rock?