Jewelery refractometer value preparation can be fixed in a range of gemstone section <br> <br> refractometer constituting the approximate refractive gemstone Crystal family Crystal system Common crystal Crystal constant characteristics Highest symmetry Advanced Crystal Group Equiaxed crystal system Diamond, garnet, spinel, fluorite, etc. a=b=c, a=β=γ=90° 3L44L36L29PC Intermediate Crystal Group Trigonal crystal system Crystal, corundum (Hongbao, Sapphire) tourmaline (tourmaline), rhodochrosite, etc. a=b≠c, a=β=γ=90° L33L23PC Quartet system Zircon, rutile, pillar stone, Fushan stone, cassiterite, etc. a=b≠c, a=β=γ=90 L44L25PC Hexagonal system Beryl, apatite, blue cone, etc. a=b≠c, a=β=90° γ=120° L66L27PC Low-level crystalline Orthorhombic system Peridot, topaz, draped stone, cordierite, emerald, andalusite, columnite, matchtop, enstatite, etc. a≠b≠c, a=β=γ=90° 3L23PC Monoclinic system Jade, nephrite, malachite, orthoclase, spodumene, etc. a≠b≠c, a=γ=90° β>90° L2PC Triclinic Plagioclase, Turquoise, Axe Stone, Rosette, etc. a≠b≠c, a≠β≠γ≠90° C 3. When the gemstone to be tested is rotated 360° on the refractometer, both shadow borders move, indicating that the gemstone is a biaxial gemstone. If the high value moves more than the median value, it indicates that the β value is close to the α value of the biaxial crystal positive light; if the low value shadow boundary moves beyond the middle value, the β value is close to the γ value of the biaxial crystal negative light. For more information on jewelry appraisal instruments and gemological specimens, please visit the official website:
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The refractometer is mainly composed of a high-refractive-index prism (lead glass or cubic zirconia), a prism mirror, a lens, a ruler (inner ruler or outer ruler), and an eyepiece.
working principle
The working principle of the refractometer is based on total internal reflection. The instrument measures the critical angle of a gemstone and converts the reading directly to a refractive index value.
Total reflection conditions:
1. The refractometer's high-refractive index prisms must be optically dense media.
2. The stones to be measured are optically sparse.
3. The contact liquid forms a good optical contact between the prism and the stone under test.
Operating procedure
1. Turn on the power and turn on the instrument.
2. Clean stones and prisms with alcohol.
3. A drop of contact liquid (appropriately 2 mm in diameter) on the refractometer prism (visible with sodium light) shows the shadow boundary of the oil.
4. The largest tabletop of the gemstone is placed on the prism, and the oil is immersed to make a good optical contact between the gemstone and the prism.
5. Eyes close to the eyepiece can observe the shadow and bright areas and take readings. The readings are kept at the third decimal place.
6. Rotate the gem 360° in sequence. Experienced ones can turn the gemstones 0°, 45°, and 90° for observation and reading.
7. After the test is completed, gently push the gemstone onto the metal table and remove the gemstone.
8. Clean gems and prisms. [3]
The main purpose
1. To identify gems, the refractive index value of gems between RI1.35-1.81 can be determined 2. Can determine the birefringence (DR) of a gem
3. Determine the gem's axial properties, such as monoaxial, biaxial, and isotropic (equiaxed, amorphous)
4. Determine the symbology of a gem, such as the anisotropy gem's positive and negative light properties
Phenomenon explanation
1. The gemstone always has only one shadow boundary (fixed) when it is rotated 360° on the refractometer, indicating that the gemstone is an isotropic gemstone (single refraction gemstone).
2. When the gemstone to be measured turns 360° on the refractometer, two shadow borders appear, one shadow border is fixed and the other one moves, indicating that the gemstone is a gemstone. If the dynamic value is a large value, it is a uniaxial crystalline gemstone; if the kinetic value is a small value, it is a gyroscopic negative gemstone.
4. Point measurement method (hyperopia art method): stones smaller <br> <br> limitation of arc-type facets and
1. The gemstone to be measured must have a polished surface 2. The RI<1.35 or>1.81 of the gem cannot read 3. It is not possible to distinguish between some artificially processed stones, such as natural sapphires and heat-treated sapphires. Cannot distinguish between certain synthetic stones, such as natural rubies and synthetic rubies
