Jasper

Jasper is an opaque form of silica, built mostly from extremely fine-grained quartz or chalcedony, and Wikipedia puts its usual reddish shade down to iron inclusions. Other minerals give it yellow, brown, green and, rarely, blue tones, and because it takes a high polish it has long been carved into seals, vases and jewellery. The name passes back through Old French and Latin to the Greek iaspis, and jasper seals were being cut on Minoan Crete around 1800 BC. Cunningham calls it a common stone whose magical history reaches back to the earliest times. He records that Native Americans used it in rain ceremonies, which he gives as the origin of its folk name rainbringer. He treats it as a guard against both bodily and unseen dangers, has it worn to aid thinking and hold back reckless impulses, and has it held during childbirth to protect mother and baby; carved jasper arrowheads, he says, are worn for luck. Hall calls jasper a nurturing stone and associates it with protection, grounding, cleansing the aura and the courage to face problems head on, adding that it works slowly and suits long use. Both writers also give separate properties for single colours, such as red, green and brown jasper.