Spinel has been praised as “the most beautiful gem” since ancient times. After molten magma flows into limestone or dolomite containing impurities, it gradually generates an ore called Spinel through metamorphism.
Spinel is mainly an octahedral crystal, occasionally with cube, rhombic dodecahedron or aggregate of granular, massive and compact crystals.
Its colors are various, such as colorless, pink, red, purplish red, light purple, blue-purple, blue, yellow, brown, etc., with white streaks and glass luster, transparent or opaque.
Spinel has always been regarded as ruby gem in past because it usually coexists with ruby and looks like ruby. Some famous rubies in history are actually spinels.
For example, Black Prince’s Ruby on the British crown and Timur Ruby embedded in a diamond chain are actually red spinels.
In the past, Spinel was called “Balas ruby.” Balas is the name of Badakshan in northern Afghanistan. The vast Spinel produced locally was regarded as a ruby during the Middle Ages. To this day, some people still call red spinel “Ruby Spinel.”
Basic properties of Spinel
- Refractive index: 1.712-1.736
- Dispersion rate: 0.026
- Relative density: 3.58-3.61
- Hardness: 8
- Chemical formula: MgOAL2O4
- Crystalline system: cubic system
Origin of Spinel Name
The origin of Spinel is still uncertain. There are two more credible versions:
one is derived from the Greek “Spark,” meaning “fire,” which describes its bright red color;
The other is from the Latin word “Spina,” which means tip. Because its crystal shape is cubic and has a sharp angle, it is named after it.
Characteristics of Spinel
Spinel has many colors, including blue, pink, green, brown, colorless and red.
It is magnesium-containing aluminum oxide (MgOAlO). The magnesium in the chemical formula is often replaced by iron or manganese. The standard coloring elements of bright red Spinel are chromium and iron.
Due to the different metal elements, the refractive index values are slightly different, but most of them are about 1.718. Only blue Spinel can reach 1.74, with a relative density of 3.58-3.61, a hardness of 8, and a dispersion index of 0.026.
In terms of inclusions, the purity of most spinels is much higher than that of corundum gemstones.
Type of Spinel
According to the different elements contained, Spinel can be divided into aluminum spinel, iron spinel, zinc spinel, manganese spinel, chromium spinel, etc.
According to their colors, there are red, blue, green, colorless, light purple, blue-purple, yellow, brown, pink, purple Spinel, etc. According to special optical effects, there are color-changing Spinel, starlight spinel and ordinary Spinel.
Spinel by color
The various red tones of red Spinel are caused by the trace element chromium contained in the Spinel, and pure red is the most precious variety in the Spinel.
Its color ranges from light pink to dark red of almandine. In addition, orange-red to orange spinel varieties are sometimes classified as red.
Blue Spinel is blue due to Zn and Fe+, and most blue spinels are from gray-blue to purple-blue with green.
The density and refractive index of blue Spinel are higher than those of ordinary Spinel.
At present, most of the synthetic products on the market are made by the Russian cosolvent method.
The green of green Spinel is generally caused by Fe3+, and the color is dark; some of them are basically black. The really black Spinel is found in Montesanma, Thailand, etc.
Colorless spinels are rare, and most natural colorless spinels have a pink tone more or less.
By optical effect
At present, the known color-changing Spinel is very rare, containing diamonds, which are blue in sunlight and purple in artificial light sources.
Starlight spinel is generally dark purple to black, and the red one is the most valuable, with a small number.
It can show four-star or six-star light, mainly because there are needle rutile inclusions inside, which are mainly found in Sri Lanka.
Value of Spinel
Even in the downturn, the market for high-quality Spinel is no lower than that in its popular period. If we compare Ruby and red Spinel with the same color and good quality, the unit price of Spinel per carat is only about 1/3 of Ruby.
Unfortunately, Even if rubies are much more expensive, but sell much faster than spinels, perhaps because people did not know the difference between rubies and spinels in the past, which led to confusion.
As a result, natural red spinels are regarded as ruby quality products, and there is a misunderstanding that “red is precious, but spinels are cheap.”
However, although the output of spinels is more than that of rubies, it may be more difficult to find really high-quality spinels than high-quality rubies.
There are artificial spinel products in the gem market. The traditional synthesis method is the fire melting method.
In recent years, Spinel synthesized by the melting method has also entered the market. The appearance and contents of artificial Spinel synthesized by the melting method are closer to natural Spinel, which is easy to cause mixing in identification.
Artificial Spinel was manufactured in the middle of the 19th century. It was originally intended to manufacture sapphire.
In order to make the crystal grow smoothly, it was necessary to add some magnesium oxide, but the Spinel was thus obtained. Since then, different trace elements have been added to produce spinels of different colors as artificial substitutes for other gemstones.
For example, sky blue artificial spinels are usually used as substitutes for sea blue gems, and pink can be used as tourmalines.
Production method of synthetic Spinel
The ratio of magnesium oxide (MgO) and aluminum oxide (A12O3) of Spinel synthesized by the flame melting method is slightly different from that of natural Spinel.
For this reason, synthetic Spinel’s refractive index and relative density are higher than those of natural Spinel.
The quality of synthetic Spinel produced by the flux method is higher than that produced by the flame melting method. Today, the products produced by the flux method are mostly used for scientific research.
How to select Spinel
1) Principles for purchasing Spinel
Color, transparency, weight and cutting are the basis for evaluating and purchasing Spinel.
The best color is bright red, followed by purplish red, orange-red, light red and blue. The first choice is the faceted Spinel with pure color, bright color, good transparency, and a good cutting ratio.
Spinel with starlight effect is also more valuable. Large and high-quality spinels are rare, and now more than 5ct, high-quality spinels are precious.
Basically, the refractive index of artificial Spinel is slightly higher than that of natural Spinel, about 1.728, but natural Spinel may also have this refractive index, so it is necessary to use other tests to separate natural and artificial spinels;
The relative density of synthetic Spinel is 3.64, which is slightly higher than that of natural Spinel.
The strong single refraction effect under polarizing microscope can provide the basis for identification.
However, the main difference is still to observe with a microscope. The difference between natural and artificial inclusions is the key to identification.
In addition, the sky blue synthetic spinel contains diamond(Co), which is red under the color filter, is also an effective identification method.
2) You should know things when purchasing Spinel
The imitations of Spinel mainly include synthetic Spinel and glass. The difference between Spinel and synthetic Spinel is that the synthetic methods of Spinel mainly include the flame dissolution method and the cosolvent method.
The intuitive identification method is that the color of synthetic Spinel is too bright, uniform, and clean, and sometimes arc-shaped growth lines, umbrella-shaped, elongated or special-shaped bubbles can be seen.
Spinel synthesized by the cosolvent method is helpful for the residual platinum metal sheet. The refractive index of synthetic Spinel is 1728, which is higher than that of natural Spinel.
Distinguish between Spinel and glass: there are bubbles in the glass, and the hardness of the glass containing mineral inclusions in Spinel is small, which is easy to cause some wear on the surface; However, the hardness of Spinel is relatively high, so it is not easy to wear.
Spinel healing property
Orange Spinel can open and adjust the umbilical wheel, stimulate creativity, enhance intuition, and balance emotions.
It is said that orange Spinel can cure infertility.
It is said that yellow Spinel can open and adjust the sun wheel to develop intelligence and personal strength.
The black Spinel has the function of protecting and stabilizing energy, which helps to promote the rise of spiritual energy.
It is said that the black Spinel can penetrate into the internal essence of the problem and help people maintain their perseverance to continue to move forward.
The red Spinel can open and adjust the sea wheel, stimulate the body’s vitality and strength, and stimulate the power.
It is said that blue Spinel can open and adjust the throat chakra, promote communication and channeling, and make people have few desires.
Green Spinel can open and adjust the heart wheel to stimulate love and kindness.
Brown Spinel can purify the aura and connect the physical body.
This kind of Spinel can open the earth’s wheel and make people make down-to-earth efforts.
It is said that Violet Spinel can open and adjust the crown wheel to promote the development of spirituality.
It is said that colorless Spinel is conducive to promoting higher-level communication and strengthening spiritual vision and understanding.
Efficacy of Spinel:
- Eliminate fatigue, help the body recover and bring vitality;
- Relieve the mood, reduce irritability, bring enthusiasm, courage and strength;
- Improve personal temperament, increase personal confidence, and maintain an optimistic attitude.
Spinel contains a variety of mineral elements needed by the human body. Wearing it for a long time can enable the human body to gradually absorb these substances, enhance vitality and vitality, eliminate fatigue, and help the body recover.
Relieve the mood
The color of the Spinel is pure and bright, which seems to give people a pleasant mood. It can strengthen the enthusiasm and courage of the wearer, enhance feelings, give determination and strength, and reduce irritability in the heart.
Spinel has a strong decorative effect. Wearing it on the wearer can enhance the charm of the wearer’s temperament, make him more confident, maintain an optimistic attitude when dealing with things, and be calm in the face of difficulties.
Spinel is an aluminum-magnesium oxide mineral, produced in marble with more magnesium components.
Pure crystals are colorless and transparent. The color of gemstones can be changed by replacing magnesium and aluminum with other components.
The Spinel containing chromium element is red. High-quality red Spinel is sometimes mistaken as ruby.
However, Spinel belongs to the octahedron of equiaxed crystal system, and ruby belongs to the trigonal crystal system. They are different.
From the mineral point of view, Spinel is a large family, but only a small part belongs to the gem-grade Spinel. Like rubies and sapphires, spinels are mostly found in river sediments, which are symbiotic minerals.
Spinel has various colors, including red, pink, rose red, blue, purple-blue, green blue, gray-green, etc., and a small amount of orange and colorless, of which red and blue are the most popular.
Rose and pink spinels are the most popular among young people today because they have high transparency and shiny luster, and They are precious gem-grade spinels.
Spinel often contains some inclusions, which are mostly small, colorless, octahedral Spinel and dark magnetite, and sometimes fingerprint gas-liquid inclusions can be seen.
The Spinel from Sri Lanka contains short columnar zircon inclusions, while the Spinel from Myanmar contains hexagonal columnar apatite inclusions. Large spinel crystals are rare.
Spinel is mainly produced in Myanmar, Sri Lanka, Afghanistan, Australia, Brazil, Nepal, Algeria, Thailand, Tanzania, and the United States.
Centuries ago, people classified red spinels as rubies. Many famous “rubies” were later found to be “spinels.” Today, the “Black Prince’s Ruby” in the center of the British Queen’s crown and another 361 carats, “Timur Ruby,” are such examples.