n.
Opaque, fine-grained or dense variety of the silica mineral chert that exhibits various colours, but chiefly brick red to brownish red.
Long used for jewelry and ornamentation, it has a dull lustre but takes a fine polish; its physical properties are those of quartz . Jasper is common and widely distributed, occurring in the Ural Mountains, North Africa, Sicily, Germany, and elsewhere. For thousands of years, black jasper was used to test gold-silver alloys for their gold content. Rubbing the alloys on the stone, called a touchstone, produces a streak the colour of which determines the gold content within 1 part in 100.