Agate is a kind of stone gem that is made of quartz and Yemeni stone and has different types and colors. Opals typically form among metamorphic and volcanic rocks. According to archaeological research, the first human use of agate dates back to the third millennium BC and the Indus Valley civilization. In ancient Greece, opals were used to make jewelry. Agate was also used to make special seals and badges for Greek warriors

Agate mineralogy

The main chemical composition of agate is Sio or silicon dioxide. Agate is a type of quartz that has a hardness of 7 according to the Mohs hardness table. Among the minerals, diamond has the highest degree of hardness with a hardness of 10 and is considered the most resistant mineral. In fact, it can be said that the original agate has a suitable hardness with a difference of 3 degrees compared to diamond. This difficulty is one of the ways of pricing agate and distinguishing the original from its imitation. For example, if you have an artificial agate ring and massage it with a rough silk cloth, it will get scratched, but the surface of the original agate will become more visible and shiny. Sometimes, in the process of agate formation, other chemical elements such as aluminum, iron, magnesium, calcium, nickel, chromium are placed next to it and enter the crystal structure of agate. This phenomenon may cause different types and colors of agate. Agate is lustrous and has a crystalline structure, and a variety of it contains a lot of mica, which is called charm. The crystal form of opal is thin and hexagonal, and this mineral dissolves in potassium hydroxide (KOH).

How to form agate

Opals are usually found in the form of grains in the cavities and pores in volcanic rocks. These holes are where the gases escape from the cooling volcanic lava, which eventually leads to the creation of a porous and porous texture in the volcanic rocks. When liquids filled with silica enter these cavities, the stages of agate formation begin. First, a thin layer of agate, commonly known as a primer or starter layer, covers the entire surface of the cavity and its internal walls, then the formation of the agate crystal structure continues slowly. The state and conditions of formation and chemical compounds in the environment cause the production of various types of agate with different characteristics, patterns and color patterns. For example, if the liquids containing silica do not completely fill the cavity, a type of agate called hollow agate is made. If, during the formation of agate, there are oxides of iron or manganese in the place, a stone with green veins called mossy agate or tree agate may be created. In addition to volcanic rocks and metamorphic rocks, opals can also form among sedimentary rocks such as dolomite and limestone. Agate formation has also been observed in the vicinity of petrified wood, remains of corpses, shells and animal fossils including gastropods and corals.

The use of agate in industry and art

Agate is used in some industries due to its very high strength and resistance and lack of reaction with chemicals. Agate is used in the production of some precise laboratory measurement and measurement equipment, laboratory mortars, and tools used in the leather industry. Agate is also used in making jewelry and ornaments such as brooches, necklaces, gold rings and in making seals and marbles.

Agate history

Theophrastus discovered this stone in the river in the 14th century, bowls and containers made of agate were very popular during the Byzantine Empire (Eastern Rome-Constantinople), and the collection of these bowls was popular among wealthy European families during the Renaissance. Today, in many museums such as the French Louvre, these made containers or bowls are very important and are kept. Agate stone is considered a semi-precious stone and is one of the minerals that is formed by the combination of several chemical elements. One of the characteristics of this mineral is its fine grain and bright color. There are various types of texture of this gem, semi-transparent, matte and with glass polish. Since three thousand years ago, the Egyptians used the properties of agate stone to make beads, and it is still very popular today. One of the unique collections known, which contains more than three thousand agate bowls, belongs to the king of Pontus, Bahram, which can be guessed from the age and the way these bowls were collected at that time, how valuable they were at that time. And they were noted, so that noble and wealthy families sought to gather their collections. The first cutting of this semi-precious gem took place in 1548 AD, but widely cutting of this beautiful gem was officially done in Germany by Idar-Oberstein from the beginning of the 16th century and has continued to this day, so that the centers "Idar" lathes are the best centers for cutting this gem and every day a large amount of precious stones from all over the world enter this center for cutting and engraving.

Types of opal stones

There are different types of this old and beautiful gem according to the shape and structure of its layers, which are as follows:

Mossy agate: it is the first type of agate that contains The green crystals are in the shape of moss.

Shajri: It is a kind of gray or colorless and semi-transparent stone with the shape of a tree carved on its surface.

Babaqouri: This type consists of parallel circular layers that have a dark colored spot in the center.

Aqueous: In this type of stone, there is some water, which is related to the time of its creation, and in thin cuttings of the stone, the water inside can be seen.
Majov: a stone that has many holes and many hollows.
Dzhi: A type of agate that has a map on it or inside it like old fortresses.
A landscape : Shapes in the form of trees and natural landscapes can be seen inside this type of gem.
Layered: In this type, the stone layers are parallel to each other. It was said that the most important models are agate stones, and we can also mention the Heli blue, Selvy purple, banded blue, and fiery models.

The variety of agate stone in terms of color

Types of agate are usually in the form of flat layers, which make them valuable due to the presence of impurities with different shapes that sometimes create an attractive view. This gem has different types in terms of color, this gem has been seen in more than 30 different colors, according to the color quality and the phenomena it shows, it is classified as a semi-precious stone. Their microscopic structure shows the presence of liquid, solid, gas, and especially the presence of color-forming metal elements such as brown, white, red, gray, pink, black and white, green, and yellow, which include a wide range of colors. Also, Yamani agate, Soleimani, etc. are other types of agate. Examples of the types of colors used in jewelry are as follows.

What is agate? Types and properties of this stone