(1) Color: The colors of spinel with high value are deep red, purple red and orange red. The values of the spinel of other colors are relative low. But the spinel with color changing effect is an exception.
(2) Defect: The spinel is usually clear with few defects. If our eyes can see the defect, crack or cleft, then its value will be greatly decreased. If there is inclusion in the spinel, so long as it does not damage the integral color of spinel, then it has little effect to the evaluation of the quality.
(3) Cut: As the color distribution of spinel is usually even and has no polychroism, we don’t need to take its directionality into consideration. But the size of crystalline of spinel is usually small and often grows spinel bicrystals and octahedral cleavage, the size of the gemstone after being cut and polished is usually not good. When evaluating, we need to pay attention to the shininess of the gemstone and leaking light or not. The less the leaking light is, the better it is; the brighter the shininess is, the better it is.
(4) Carat: For the high-quality spinel, the ones with the weight over 10 carats are very few. So when cutting, we need to decrease the loss as much as possible to keep the carat of original stone.