Mineralogists qualitatively classify 10 standard minerals according to their relative hardness, and the hardness decreases from 10 to 1. The hardest gem in the world is diamond, the hardness is 10, and the hardness of sapphire is second only to that of diamond. Enough to prove how hard sapphire is.

The reason why the hardness of sapphire can firmly position sapphire in the gem world is because hardness is the basis for dividing high-grade and low-grade jewelry and jade. The internationally recognized hardness of high-grade gemstones is not low, such as 10 for diamonds, 7.5-8 for emeralds, 8-8.5 for gold emeralds and 9 for rubies. They are all one of the five precious stones, from which we can see that hardness is the positioning of high-grade precious stones.

Characteristics of sapphire:

Sapphire is characterized by uneven color, and parallel hexagonal columns are arranged with flat bands and growth lines of different shades. Double crystals are developed in multilayer plates, which are usually louver-shaped, and cleavage often splits along the double crystal plane. Regarding the collection value of sapphire, the quality of sapphire is the key, which can be compared mainly from the aspects of color, clarity, weight and cutting.

Kashmir sapphire is a kind of high-quality sapphire, which is called cornflower blue by the jewelry industry. It is bright and pleasing to the eye because it contains tiny dust-like inclusions, which scatter light and form a velvet luster.