A grain of cinnabar means a grain of cinnabar ore.

Cinnabar, also known as cinnabar, cinnabar, red cinnabar, and mercury sand, is a mercury sulfide (HgS) mineral. Often rhombohedral or short columnar; common through twin crystals. Complete cleavage with parallel cylinders. The aggregates are granular, massive or film-like. Mohs hardness 2.5, specific gravity 8.10. Pure cinnabar has a diamond luster and vermilion color; when it contains impurities, its luster is dim and brownish red. It is a typical low-temperature hydrothermal mineral, and its origin is related to modern volcanism.

Containing 86.2% mercury, it is the main mineral raw material for mercury refining; its crystals can be used as important materials in laser technology. It is also a Chinese medicinal material with sedative, soothing and sterilizing effects. Ancient China used it as an important raw material for alchemy. In the past, it was named after the best quality produced in Chenzhou (now Yuanling, Hunan and other places).

Extended information:

Introduction to cinnabar:

Natural cinnabar is a granular or massive aggregate, in the form of patches or fine grains of different sizes. The surface of the larger pieces is dark red, the surface of the small flakes or granules is bright red, and the irregular flakes are bright red in color, as bright as a mirror, do not stain the hand when touched, have a diamond luster, and are translucent. Crisp, hardness 2-2.5, specific gravity 8.09-8.20, streaks vermilion to brown.

Synthetic cinnabar is in the form of purple-red irregular blocks or vermilion granules and powder. It is insoluble in strong acid and soluble in sodium sulfide and aqua regia. When heated in a closed test tube, it turns into a black vulcanization pump; when sodium carbonate is added and heated, it turns into a metallic mercury ball. When burned in an open tube, sulfur dioxide gas and metallic mercury balls are produced. After soaking the fine powder with hydrochloric acid, rub it on a smooth copper sheet. The surface of the copper sheet will appear silvery white.

The crystal belongs to the trigonal crystal system and is homogeneous with the black cinnabar of the equiaxed crystal system. Often rhombohedral or short columnar; common through twin crystals. Complete cleavage with parallel cylinders. The aggregates are granular, massive or film-like. Mohs hardness 2.5, specific gravity 8.10. The color is often red, and the crystal surface has red streaks and is translucent.

Pure cinnabar has a diamond luster and vermilion color; when it contains impurities, it has a dull luster and is brownish red. It is a typical low-temperature hydrothermal mineral, and its origin is related to modern volcanism. China is the main producer of cinnabar, with Xinhuang, Hunan, and Tongren, Guizhou being the main producing areas.

Other producing areas in the world include Almaden in Spain, Udrià in Italy, and the coastal mountains of California in the United States. The crystal shape is plate-like or columnar, and interspersed twin crystals are common. Cleavage development. The hardness is small, 2~2.5. The specific gravity is larger, 8.09. The powder of cinnabar is red and can last for a long time;

my country has a long history of using cinnabar as a pigment.

Applying vermilion to oracle bones, grinding cinnabar into red powder and embedding it in the inscriptions of oracle bones to make them stand out, happened thousands of years ago; emperors of all dynasties in feudal society used the red pen to write their approvals using the red powder of cinnabar for the purpose of looking at them. Eye-catching and long-term preservation

Baidu Encyclopedia-cinnabar (mercury sulfide mineral)

Baidu Encyclopedia-cinnabar