Broadly speaking, all red gems may become imitations of rubies, but the gems similar to rubies in appearance mainly include red spinel, red garnet, red tourmaline, red beryl, red zircon, andalusite and red glass.

Table C- List of physical characteristics of rubies and imitation gems

0.008 single refraction octahedral crystal inclusions and negative crystals in single refraction 0.014-0.0200.004-0.090.0590.010 single refraction [align=center] spinel [/align] [TD = 65438]

The color characteristics of blue cone ore are similar to sapphire, but it has strong polychromatic color. Usually the top facet is blue, and the parallel waist edge is colorless, which is obviously different from sapphire blue green or green blue. The birefringence of blue cone ore is very large, reaching 0.047, and it is positive. Under the microscope, the double image of faceted edge is obvious. The dispersion of blue cone ore is very strong (0.046). Although it is partially covered by body color, the well-cut blue cone mine presents a realistic appearance. In addition, blue cone ore has bright blue fluorescence under short-wave ultraviolet irradiation, while sapphire is inert or weak fluorescence.

(3) the difference with cordierite

Cordierite has a low refractive index (1.54- 1.55), and the surface luster of the gemstone is weaker than that of sapphire, and its relative density (2.65) is small. It floats in a heavy liquid of 3.32, and the sapphire sinks. Visible to the naked eye obvious polychromatic, the top facet is usually blue, and the other two directions are blue-purple and light yellow. Unlike sapphire, cordierite may have absorption bands in yellow region, green region and blue-purple region.

[table = 98%] [tr] [TD] [align = center] [img]/Albums/ee62/jewelry 66/Ding Jian/jian3/3-2-38.jpg [/img] [/align] [/TD] [/tr] [tr].

(4) The difference with zoisite.

[table = 98%] [tr] [TD] [align = center] [img]/Albums/ee62/jewelry 66/Ding Jian/jian3/3-2-39.gif [/img] [/align] [/TD] [/tr] [tr]. [/td][/tr][/table] zoisite's blue-purple variety is tanzanite, which has strong trichromaticity, namely blue, magenta and green, while zoisite's relative density (3.35) is lower than that of sapphire, which slowly sinks in a heavy liquid of 3.32, while sapphire sinks quickly. Refractive index test can also be distinguished from sapphire.

The difference between tourmaline and glass is similar to ruby.