As we all know, diamonds are known as the most precious gemstone variety in the world and the "king of gems" for their crystal clear, dazzling and unparalleled hardness. How are diamonds formed? What are the diamond identification methods? The following is my method of sorting out and identifying diamonds. Welcome to reading.

How are diamonds formed? Diamonds are usually formed by volcanic eruptions and brought to the earth's surface by magma. Magma will also capture some related minerals to the earth's surface during its ascent. These will be "indicative" minerals used to find diamonds. In the same soil range, the more indicator minerals there are, the greater the chance of finding diamonds.

According to the study of inclusions, the diamond formation temperature is 900- 1300℃ and the pressure is 45-60× 108Pa, which is equivalent to 130- 180km deep in the earth. According to the age analysis of the package, the age of diamond formation is usually much earlier than kimberlite or lamprophyre that brought it to the surface, such as kimberlite diamond mine in South Africa. Kimberlite was formed before 90-1000 ma, but the diamonds in this mine were formed before 3300 Ma. Diamond mines all over the world have the same characteristics. Therefore, it can be considered that diamonds were formed in the depths of the mantle in an ancient geological history. In the later volcanic activity, it was captured by kimberlite magma or K-Mg lamprophyre magma, brought to the surface, found in kimberlite and K-Mg lamprophyre, and formed diamond primary ore.

After weathering and denudation of primary ore, diamonds are taken to rivers or coastal environments for deposition, forming secondary placer of diamonds. As of 187 1, all the diamonds in the world are found in secondary placer, which is still the main source of diamonds in the world. The first primary diamond mine was discovered in Kimberly, South Africa in 1870. Later, kimberlite or K-Mg lamprophyre primary diamond deposits were discovered in Botswana, Zaire, Australia, Russia, Brazil and China.

Physical effects of diamonds Chinese name: diamonds, diamonds

English name: Diamond

Mohs hardness: 10

Chemical composition: 99.98% carbon.

Physical efficacy: It has the highest hardness among natural minerals, and its brittleness is also quite high, and it will still be broken by hard collision. From the ancient Greek agonist, which means hard and inviolable substance, it is recognized as the king of gems. In other words, diamond is actually a kind of carbon crystal with quite high density.

Common shapes: round, oval, olive pointed, heart-shaped, pear-shaped, square, triangle, emerald-shaped. A round drill is the most common shape.

Refractive index: 2.4 17

Dispersion value: 0.044*** higher * * *

Total internal reflection: critical angle: 24.5.

Main producing areas: The main producing areas of diamonds are Australia, Botswana, Canada, Zimbabwe, Namibia, South Africa, Brazil and Siberia; At present, the main diamond cutting and grinding centers in the world are Antwerp, Tel Aviv, new york, Mumbai, Thailand and Bangkok. Antwerp has the reputation of "the diamond capital of the world", where about half of the world's diamond transactions are completed. "Antwerp Cutting" is synonymous with perfect cut.

Diamonds are extremely precious, so their weight is expressed in a special unit carat. 1 carat equals 0.2 grams. At present, the largest diamond in the world is a diamond named Africa Star, which is embedded in the Queen's scepter and weighs 530.2 carats, or 106.04 grams.

Simple identification of diamond identification methods

Simple identification method of diamonds: you need a magnifying glass of 10-20 times as an aid to make a few simple observations.

Observe the waist of the diamond. If it has a frosted waistline, this method is most suitable. Because diamonds are harder than any imitations, they don't have thin lines like imitations, and the waistline of diamonds has a granular appearance.

Diamonds are harder than imitations, and the faceted edges of imitations are often duller than diamonds. The faceted edges of diamonds must be sharp.

Because diamonds are harder than imitations, the faceted edges of imitations often wear out.

If a diamond has a natural surface, there is a chance to find a unique "triangular growth line" on the natural surface.

If a diamond is broken, its appearance is usually stepped, while the imitation will be completely bent or shell-shaped.

hardness testing

Diamond is the hardest natural substance known, and nothing can mark it. If you can mark it, it's definitely not a diamond.

Thermal conductivity test

At the same time, breathe into the diamonds and other similar objects to be debated. If it is a diamond, the water mist condensed on its surface should evaporate faster than other objects, because the thermal conductivity of the diamond is high.

observational method

Observe reflected light

With a magnifying glass, it can be observed that the waist of the diamond presents a very fine matte shape, and the reflected light shines. This characteristic of diamonds is unique.

Look at the growing point

Observing under a magnifying glass, there are often grooves and triangular growth points on the crystal face of real diamonds, but there are three kinds of fakes: ① Ordinary glass with alumina is easy to get into the wrong place, because the refractive index and dispersion increase, but the hardness is lower. (2) Imitated with chemically synthesized sapphire and colorless spinel, the hardness is similar, but the refractive index is low and has birefringence, and the double image can be seen under a magnifying glass.

Pencil mark

The chemical composition of pencils is carbon, just like diamonds, but the physical structure is different, so many people use pencils to detect the authenticity of diamonds, which is a practical and effective method. When identifying, the diamond should be wetted with water first, and then gently scratched with a pencil. On the crystal face of a real diamond, there is no trace where the pencil crosses, but if it is not a diamond, but a material such as glass and crystal, it will leave a trace on the surface. Generally, it has high hardness and good refraction, but it will reflect more colored light when rotating, which is obviously different from the genuine product that only reflects weak yellow-blue light when rotating.