Shaped like inside-out umbrellas, they produce the crimson resin, known as "cinnabar", that Roman gladiators once used to protect themselves from infection.Other strange plants, which elsewhere have been grazed to extinction, still thrive on Socotra, oozing aloes that the native Socotrans cultivate as cosmetics and herbal remedies.
Silver, cinnabar, and coal are mined nearby.
Other mineral products include antimony, tungsten, mercury, phosphorus, silver, placer gold, cinnabar (the ore of mercury), and manganese.
The red lacquer (tihong), so well known and justly appreciated, was coloured with cinnabar (red mercuric sulfide).
The principal ore is the red sulfide, cinnabar.
Calomel (Hg2Cl2), also called mercurous chloride or mercury(I) chloride, a very heavy, soft, white, odourless, and tasteless halide mineral formed by the alteration of other mercury minerals, such as cinnabar or amalgams.
The nonopaque varieties (e.g., cinnabar, realgar, and orpiment) possess high refractive indices, transmitting light only on the thin edges of a specimen.
Throughout history, cinnabar has been used as a pigment or colouring because of its attractive red colour, and in the 19th century some American Indians in California complained of illness that was diagnosed as mercury poisoning caused by cinnabar in war paint.
Mercury is extracted from cinnabar by roasting it in air, followed by condensation of the mercury vapour.
By 100 bc mercury was known and was produced by heating the sulfide mineral cinnabar and condensing the vapours.
