In gemmology, a magnifying glass (represented by "10×") with a magnification of10 is generally used, and the triple combination mirror is the most commonly used. Its structure is that two convex and concave lenses made of lead-free glass are bonded in the center. In the national standard, there are clear standards for the classification of some jewels, jade and antiques, provided that they are "under a ten-fold magnifying glass".

The working distance between the magnifying glass and the test sample depends on the magnification. If the magnification is too large, the working distance will be smaller, the operation will be inconvenient and the field of vision will be narrow. This is another reason for choosing to use 10× magnifying glass in gemology. Gemstone magnifying glass is characterized by wide field of view, which eliminates image distortion and dispersion, that is, there is no aberration and chromatic aberration.

Extended data:

Gem magnifying glass application

1, observation of surface characteristics of gemstones

(1) Gemstone luster

If the luster of the crown and pavilion of the gem is different, it may be inlaid stone; Different gem varieties have their own unique luster, such as diamond luster, colorless corundum luster for glass and so on.

(2) Sharpness of gemstone facet edge

If the facet of a gem is sharp and straight, it means it is very hard. For example, the faceted edges of diamonds are always sharp and straight, while imitation diamonds are smooth.

(3) The original crystal plane, cleavage and fracture characteristics of the gem.

If there are multiple groups of flat textures on the surface and stepped sections, cleavage is developed, and if there is conchoidal fracture, it may be a single crystal gem or glass imitation; If there are soil-like and granular fractures, it may be a multi-quality aggregate; Bitter gem has original crystal plane, which means it is a natural gem.

(4) Cutting quality and polishing quality of gemstones

Observe whether the proportion of each part of the gem is appropriate, whether the proportion and symmetry are intact, and whether the facets are symmetrical and equal. How smooth is the surface of the gem, whether there are grinding marks, burning gangrene, etc.

(5) Surface defects of gemstones

Observe whether the surface of the gem is damaged, scratched, pitted and cracked.

2. Observe the internal characteristics of gems.

(1) band, growth line

If you see the ribbon bending, it shows that it is a synthetic product. Such as synthetic sapphire.

(2) The ghost of the posterior facet edge

If you see the ghost of the back facet, it means that it is a gem with large birefringence. Such as olivine, old stone, etc.

(3) inclusiveness

If you see mineral inclusions, it means they are natural gems; If you see bubbles, it means they are artificial. According to the observed characteristics of inclusions, the origin information of gems can be provided. For example, the emerald in Sri Lanka has gas, liquid and solid inclusions.

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