The price of any precious mineral consists of three criteria—beauty,rarity and durability.Demantoid wins on all counts.First—rare color,which no stone has.Second—demantoids occur,perhaps,even rarer than emeralds.Third—he has hardness7according to the Mohs scale and the absence of cleavage,that is,ability to chip in certain directions.This ensures durability.The shine of the demantoid is higher,than a diamond,it sparkles in the twilight.There are also byssolite inclusions in the stone .,divergent,like the sun's rays,or individual fibers and enhancing its shine.This feature is present only in demantoid species of the Urals.Besides,stones found in Iran,in Africa and Madagascar.The thicker the greens,the more valuable the mineral is.Ural demantoids of rich green color are the highest in quality and cost.,least—pale-green stones,with a light green or brownish tint.