The appellation agate refers only to translucent chalcedony whose color is distributed in curvilinear bands or in layers.
Agate is formed thanks to the circulation of underground water close to a saturation of silicon, thus filling the cavity of a rock or dissolving some pre-existing material such as bones or shells. As a consequence of this, the agate is frequently found in a state of rounded nodules with concentric bands like those of a tree trunk.
These bands sometimes resemble eyes, shells or even landscapes with trees and branches. This last variety is called “moss agate”.
The name of agate comes, through Latin, from a Greek word that designates the river “Achates”, in Sicily where this material was found in large quantities at that time.
Agate was one of the first materials known to man and according to legends, it returned to its friendly and persuasive wearer. It has been said that agate relieved insomnia and provided sweet dreams.
The Sumerians were perhaps the first to use agate to make stamps, necklaces, seal rings, and other jewelry. The famous collection of two thousand to four thousand glasses accumulated by Mithridates, King of Pontus, shows to what degree this mineral was appreciated. Agate cups were also very common during Byzantine times, as well as later, during the Renaissance in Europe, they were collected by the nobility. Many European museums have magnificent specimens.
The Persians, Arabs and other peoples of the East used agate, mainly as seal rings, on which was engraved a verse from the Koran, the name of its owner or some symbol or magic formula that protected its wearer from a large quantity of evils.
Agate mining in the Nahe river valley has resulted in the Idar-Oberstein quarry in Germany.
At first the river was used to power the wheels and thus extract the mineral.
When the deposits of this river were exhausted, the quarries of Idar began to exploit the agate deposits of Brazil, and also discovered the rich deposits of amethyst, topaz and other gems of this country.
The small town of Idar-Oberstein is still known throughout the world for its fine engraved agate sculptures.
Other important producers besides Brazil are India, China, Iceland, and the United States. Moss agate is found primarily in India and the United States.
Due to its porous nature, gray and white agate is susceptible to being dyed in different colors.
Variety of quartz, hard, translucent and with layers of various colors, widely used in jewelry.
- Color : Translucent with colored bands
- Family: Chalcedony – Microcrystalline Quartz
- Chemical composition: SiO2
- Crystalline system: Hexagonal
- Hardness (Mohs scale): 6.5 – 7
- Specific gravity: 2.60 ± 0.05
- Refractive index: 1.537 ± 0.02
- Birefringence: Invisible
- Optical character: Conglomerate