What is Agate?
Agate is a form of microcrystalline quartz commonly tumbled and made into jewelry and other ornamental items. It is considered a semi-precious stone. It is naturally beautiful and comes in a variety of colors that makes it appealing to a broad spectrum of collectors and gemstone enthusiasts.
What is truly interesting about agate are the concentric layers of the mineralization that results in the characteristic banded layers of the quartz. This semiprecious stone occurs in multiple colors, from yellow, brown, pink, white, black, and gray.
The colors of agate occur because of select impurities that arise in the chemical structure of the stone. Changes in the chemical formation of gemstones also have an impact on their crystallization and subsequent coloration.
It has been said that the changes in the color banding of agate occur when the water chemistry during crystallization changes. Since these are naturally formed semiprecious stones, there is no telling what type of patterning will happen as geologic processes form the agate.
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Types of Agate
How many colors of agate are there in the world?
The known permutations of agate color are nearly endless. However, there are some kind of agate that are well-known in the jewelry world.
Onyx agate refers to a subtype of agate that has curved bands. Non-onyx agate has parallel bands of color, while onyx has curvy and concentric bands that go whatever way it pleases when you cut an onyx gem into two.
An onyx agate is not just black and white, the concentric but curvy bands in the gem can be composed of other colors like brown or pink. The differentiator is always how the groups are formed. Both agate and onyx agate are chalcedony mineralization.
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Fire agate is a particular type of agate that has so far been found only in Mexico, specifically in the southern and northern mining locales and in select areas in the United States (specifically, Arizona, California, and New Mexico). The rarity of fire agate has raised its value, comparatively speaking. It’s been said that much of the fire agate that is being unearthed now were formed millions of years ago by tremendous and violent volcanic activity.
Boiling water that contained minerals filled the cracks and cavities of rocks, and the repeated washing and flooding created these unusual agates. Fire agates have a banded rainbow effect, and some of these gems score a solid seven on the Mohs scale, which makes them a little more scratch-resistant than other minerals.
Unlike other agate, the fire agate is resplendent with the Schiller effect, which it shares with a most unlikely precious material – mother of pearl. The mother of pearl is the material produced by oysters to manufacture pearls.
Moss agate is a type of chalcedony that features predominantly green colors. The green coloration is present in filament formations, and the field is comprised of either milky or clear compositions of quartz that offset the green color.
Oxides of either iron or manganese can be found in moss agate. The inclusions in moss agate, due to their spread and shape, look like regular moss that grows on stone and concrete. However, moss agate actually does not contain moss or any organic matter.
Crazy Lace Agate
Crazy lace agate is so-called because of its intricate banded patterns found throughout each sample. Also known as the Mexican agate. Usually, agate bands are simple and emanate from a single point. It can have multiple “centers” from whence the banded patterns can originate from. Multiple colors can emerge from the natural processes of creation, which makes agate diverse as a gemstone.
Blue Lace Agate
Blue lace agate is popular for its light blue soothing colors and gentle banding pattern that usually runs from top to bottom. Blue lace agate was first mined and recognized in ancient Italy.
Blue agate is astrologically linked with the Gemini zodiac sign, but it is not an official birthstone for any month. This means you can associate with it if you want – there’s no one stopping you! Blue agate is a pigmented type of agate. Labs use a special dye made of iron to create consistent blue coloration throughout the agate stone.
Iris agate is a type of chalcedony with a most striking banded pattern. A particular diffraction pattern becomes apparent when an intense, natural light hits iris agate. A multitude of bands of every conceivable color, including reds and yellows, are diffracted with a “grating effect,” as if additional mineralization prevents light from passing through. Iris agate is unique because other agates will not show this exact effect.
Sardonyx agate is a combination of onyx banding formations and sard. Some sardonyx samples appear with bright orange colors, but for the most part, you will see whites, browns, and blacks in sardonyx agate. Deposits of this chalcedony type can be found in countries like Brazil, Madagascar, the United States, and Uruguay. The ideal sardonyx is located in India, and samples take here present vibrant and striking colors as well as sharp banded patterns.
Where Are Agates Found?
Agate is extensively mined in many regions of the world, but most notably in the USA, where large agate mines are present in many locales, from Montana to Oregon. Agate is usually found in places where lava used to flow – it forms in the cavities of cooling lava. Water carries the silicates necessary for the crystallization of the agate, and lava contributes to the high temperatures and pressure required for the crystallization to occur.