Transparency can be used to understand the quality of gems. Generally speaking, the higher the transparency of the same gem, the more precious it is. Transparency can also be used to distinguish gems with similar colors but different kinds. For example, spinel and cinnabar root are similar in color, but spinel is transparent, and some cinnabar roots are opaque or translucent. So are topaz and sapphire. Topaz is a transparent crystal, and sapphire is divided into transparent, translucent and opaque. Olivine is a transparent crystal, while some jasper varieties with similar colors are opaque.
2. Look at the luster
The luster of gemstones is an important basis for naked eye identification, and a satisfactory refractive range can be roughly judged. Gloss is determined by refractive index and smoothness of polished surface. The stronger the luster of an unknown gem, the higher the refractive index. The refractive index of semi-diamond luster gemstones belongs to the high refractive index range on the refractometer scale, while the refractive index of glass luster gemstones is in the friction range, while the refractive index of semi-non-working luster gemstones is in the lower range.
Waxy and shiny jade has poor polishing surface, and silky luster indicates that there are many needle-like inclusions in the gem. Amber may have a resinous luster, and when it is cut into curved surfaces, it may be colored, translucent and turbid. The sky blue and milky luster is the ice moonstone. Sodium moonstone with pearl luster and elongated moonstone with yellow-brown and blue luster. It is the sunshine stone that glows golden in the sun. Diamonds have a typical diamond luster.
Step 3 look at the deviation
In transparent turning stones, dispersion intensity can provide important clues for identification. Only diamonds, artificial cubic zirconia, zircon, rutile, garnet and cassiterite can be seen with the naked eye. The complete spectral color of a gem is directly proportional to its dispersion, that is, a gem with high dispersion can observe the complete spectral color, and vice versa.
4. Look at this crack
Identifying some precious stones is particularly important for fracture and fracture luster. The stones with glass luster are mostly conchoidal fracture, while the translucent and opaque jade are mostly granular and hackly fracture. For example, the fracture of coral is dull and jagged; The fracture of amber is resin luster and conchoidal fracture; The fracture of chalcedony and agate is resin luster and conchoidal fracture; Turquoise has a dull oily luster and is granular or conchoidal fracture; Miyu and Dongling stone are granular and serrated faults.
5. Look at the discoloration effect. Discoloration effect refers to some gem varieties containing chromium or vanadium. Under the irradiation of different light sources, gems show different colors. For example, emerald containing chromium is green under sunlight and red under incandescent lamp, so it is also called metamorphic rock.
Gems with color-changing effect (including artificial gem) mainly include metamorphic rocks, color-changing sapphires, color-changing spinels, artificial color-changing sapphires, artificial color-changing yttrium aluminum garnet, artificial color-changing cubic zirconia and so on.
6. Look at the red flash effect. The red flash effect refers to the phenomenon that blue or green gems containing chromium, vanadium or cobalt are accompanied by red flash when illuminated by a spotlight flashlight in the dark.
The red flash effect is rare, which is one of the effective methods to distinguish some natural gems from synthetic gems. There are not many gems with red flashing effect, except garnet above and two-component stone with red glass below, which can be seen outside the red circle at the waist; There are mainly blue synthetic spinel, artificial green yttrium aluminum garnet and synthetic emerald.
Extended data
Identify the authenticity of the authentication certificate:
The first is to see if the inspection agency is legal. The state has strict qualification requirements for jewelry and jade quality appraisal institutions, and the appraisal certificate issued is only valid if it passes the review. CMA, CAL and CNAS are common in the certificate of jewelry and jade appraisal.
The second is to look at the content of the exam. Including the name, color, purity, total mass, density, refractive index and other items of the goods submitted for inspection, these items are very strict in the nationally certified jewelry and jade testing institutions.
Third, look at the signature of the appraiser. The appraisal certificate must be signed by two appraisers to be valid: one is the appraiser and the other is the reviewer. In the meantime, I have to look at the seal. Strictly speaking, it should be a steel seal, and the font on it can be clearly recognized.
Finally, look at the numbers. There is the serial number of this certificate on the back of the appraisal certificate, which should be consistent with the serial number posted on the back of the physical object. In addition, some certificates have numbers, which can be queried on the website or through SMS. If it is genuine, you can definitely find the style you bought by entering the number. Some organizations also have special anti-counterfeiting measures. For example, the certificate issued by Guangzhou Zhonggong Jewelry Testing Center has special shading and anti-counterfeiting marks.
China Work Network for Combating Infringement and Counterfeiting-How to Identify the Authenticity of Jewelry Certificates and the Method of Identifying the Authenticity of Jewelry
People's Daily Online-False certificates of jewelry and jade emerge one after another. Experts teach you how to identify the authenticity of certificates with the naked eye.