Gems similar to moonstone mainly include white quartz cat's eye, chalcedony, white opal, glass, plastic and so on. The important difference between moonstone and them is: 1. The aura of moonstone is extremely special. When turning a gem, it is often a flaky movement, while the quartz cat's eye is a linear movement. 2. Feldspar has obvious cleavage, and hackly fracture can be seen on some tiny sections, while other similar gems are mostly conchoidal fracture with smooth cambered surfaces. 3. "Hundred feet" inclusions sometimes appear in moonstone, which can be used as an important basis for identification. When the above characteristics are not obvious, it is necessary to distinguish them by measuring the refractive index and specific gravity of gems. Identify key typical cleavage and characteristic inclusions. In essence, the identification method of moonstone is based on the unique characteristics of gemstones, such as color, transparency, luster, hardness, specific gravity, inclusion, dispersion, cleavage, fracture, birefringence, special optical effect and so on. , and identified with simple tools such as magnifying glass and spotlight flashlight with magnification of 10. The theoretical basis of naked eye identification is that different gems have different characteristics in appearance and physical properties. Most gems can be divided into a rough range according to some characteristics, and experienced people can narrow this range to two or three or even determine it accurately. For example, in the current market, some people mistake Ma Laiyu and chrysoprase for high-grade jadeite; Red spinel such as ruby; Man-made products are natural products ... in fact, as long as you master the characteristics of gems, you can accurately identify them without using or using less identification equipment. The methods of identifying gems with naked eyes are introduced as follows:

Look at this color.

The first thing to pay attention to is to observe the color of the gem. No matter what kind of gem it is, with the different color and tone of the gem, the scope of identification is somewhat narrowed. The special olive green of olivine makes us feel at home. A few gems are bright emeralds, such as emeralds, garnets and some dyed gems. Black gems are only Wugang stone, coal crystal, tourmaline, diopside and biotite. Purple gemstones include amethyst, purple sapphire, spinel and cubic zirconia. When distinguishing jadeite, Malaysian jade and chrysotile, if carefully observed, we can find that jadeite is unevenly distributed in green, its fracture is dim and serrated, Malaysian jade is filiform in color, its fracture is glassy and sandy, and chrysotile is ivory and evenly distributed. Dyed jadeite is unnatural in color and concentrated in cracks, while true jadeite is natural in color and distribution. The naked eye identification of ruby and spinel shows that ruby is somewhat multicolored, and sometimes hexagonal ribbons can be seen when placed in water, while red spinel is absolutely uniform in color.

Look at transparency

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.

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.

hardness testing

Some gems with similar appearance can be distinguished by testing their hardness. Such as diamond, zircon, crystal, etc. Although the appearance is similar, the hardness is different. Diamonds can scratch zircon and crystals, but crystals can't scratch zircon. Another example is ruby, spinel, tourmaline, purple tooth black and so on. They are all red gems. Knowing their hardness differences, we can compare and distinguish them by carving. The hardness of main gemstones is as follows: diamond-10, ruby -9, golden green cat's eye -8.5, spinel -8, topaz -8, zircon -7.5-8, emerald -7.5 and tourmaline-7.5; Crystal -7, Lithospermum -6.5-7.5, Olivine -6.5-7, Opal -5.5. The following points should be paid attention to when distinguishing gems by hardness: This method has two limitations. First, some gems with similar colors have similar hardness, such as zircon and purple tooth black; Secondly, there is nothing we can do about artificial gem, because artificial gem is very similar to natural gemstones in physical properties. Don't push too hard when testing, especially don't knock and grade, but drag and grade slowly. Don't test from only one direction, but from different directions, because the hardness of gemstones in different directions is different. For example, kyanite has a hardness of 4.5 degrees in terms of crystal elongation, which can be carved with a knife, but the hardness in the direction perpendicular to it is as high as 6 degrees or more. Gems, especially gems, can't be carved casually. A safer and more reliable method is to use ground mineral polishing sheets to test. For example, to distinguish the authenticity of a warping stone, it can be used to carve an artificial spinel polishing sheet (hardness 8). If it can mark synthetic spinel, its hardness must be above 8 degrees, which may be ruby.

proportion

It is a secret skill for an experienced appraiser to weigh a gem by hand and estimate its proportion. It takes more practice to master them. For example, the ratio of diamond to colorless artificial cubic zirconia is similar to that of diamond with naked eyes, and the ratio of cubic zirconia is 5.8. The ring surface of the same size is weighed by hand, and the lighter one is diamond. Or look at the diameter of the inverted gem, and you can roughly estimate the specific gravity and weight of the gem by hand. If conditions permit, you can use the scales repeatedly used by jewelry stores to determine the specific gravity. Hang a small blue made of thin gold wire or copper wire at one end, first put the gem into the basket and weigh it in the air, that is, the weight of the gem in the air. Then, after the sapphire is immersed in glass filled with water, its weight is reduced, which is the weight of the gem in water. At this time, according to the principle of physics, the weight lost by an object in water is equal to the weight of the same volume of water discharged by the object (but the water used is based on 15℃ or 60F distilled water). So the formula is as follows: specific gravity = weight in air/weight in air-weight in water. Then, according to the specific gravity of the gem, find out the corresponding gem name in the specific gravity table. There are many corresponding gems, but the names of gems can be determined by comprehensive analysis of hardness and color. Another reliable method is the heavy liquid method, which is to mix the liquid with the same specific gravity as the gem to be measured, and then put the gem into the liquid to see if it sinks or floats. For example, the proportion of jadeite is 3.33. If it is placed in 3.2 grams of heavy liquid per cubic centimeter, jadeite will naturally sink because its specific gravity is greater than that of heavy liquid. If it floats, it is not jade. Of course, the preparation of heavy liquid needs certain raw materials, and it is not easy to operate.

Observation of inclusions

It is the most reliable method to distinguish natural and artificial products by observing the characteristics of inclusions in transparent gems with a magnifying glass of 10 times. The inclusions in natural gemstones can be solid, liquid and gas, and most of the solids are in crystal form. There are many bubbles in artificial gem, and the swirling solid inclusions are inclusions of synthetic gems.

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.

Look at this crack and cleavage

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. Cleavage is also one of the bases for gem identification, and only a few gems have obvious cleavage, such as diamonds and topaz.

Birefringence and polychromatic

With a magnifying glass of 10 times, we can see the ghost of the edge of a partially inverted transparent gem, which is also an important basis for identifying gems. Common gemstones with strong double shadow properties are zircon, olivine, tourmaline and rutile. Part of colored gems's dichroism can be seen with naked eyes. Blue-green and brown-green dichroism of tourmaline, as well as ruby, sapphire, zircon, andalusite and metamorphic rocks. You can see clearly by turning the gem.

Look at the special optical effects

Some gems have special optical effects, and the appearance of any optical phenomenon may narrow the prediction range of unknown gems. Place the upside-down gem on a white background, and illuminate the bottom of the sample from different angles with a pen cylinder. If you see a circle of red around the flat bottom or waist, it may be purple tooth black or glass double stone. Please note that red circles are not visible for red, purple or thin samples. It emits a deep red tone from a bright blue gem and can be considered as synthetic spinel or Tanzanite. Individual gems will change color under different light sources. Stone is purple-blue in natural light and red-purple in tungsten lamp. Glauconite halo will change color under different light. Opal has a special multicolor change. Snowflakes often flash in aquamarine. Common shore-borne gems are ruby, sapphire, hibiscus stone and purple tooth black. There are spinel, pyroxene and amphibole. If one gem is thin and obvious, the other is wide and fuzzy, and many metal inclusions can be seen under the magnifying glass, it is diopside starlight gem. Common cat's eye gems are emerald, crystal, aquamarine, tourmaline, feldspar and so on. And those who swim like tiger eyes and eagle eyes have turned into wood.