They are synthetic stone. They are highly esteemed since ancient times, along with diamond and emerald are considered the most valuable among the precious stones. All corundum gem, except red, is called sapphire (fantasy sapphires), specifying the colour, for example yellow sapphire. However, in commercial language it is known that sapphire is blue and synthetic sapphire price is not very high. The rubies adopt different shades of red; the intense red is called "pigeon blood" and is the most valuable.