In terms of scale, crystal imps stand about 2 feet tall, not counting their horns. Their colouration is indicative of the mineral content where they were born. Ametrine quartz and rock quartz are the two most common formations large enough to host a warren of imps, and canny surveyors can determine what sorts of valuable minerals might be around based in the colouration of local imps. However when crystal imps are around, a lot of other things go missing, like unattended cookies.