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Agate Properties Facts and Photos

Agate stone with colourful banding. A museum exhibit on a blackened background

1. The History of Agate
2. What is Agate?
3. Natural Agate Types
4. A Few More Facts
5. Agate Healing Properties
6. Article Pictures
7. Shop for Agate

History of the Mineral Agate

Agate was highly valued by many ancient cultures including the Sumerians, Egyptians, Greeks and Romans.  It was widely used for talismans, seals, vessels (container for liquids), beads and gemstones.

One of the oldest of all minerals, references to agate can be traced back more than 2000 years to the writings of Ancient Greek philosopher Theophrastus [c.370-285 BC].   The process of describing different agate types and their meanings can be found in his works Theophrastus On Stones.  In this reference he compares the hardness of agate to onyx and talks about how one type differs from the other because of "its irregular and uncertain manner of spots, clouds and variegations".

He says although agate stone is predominantly grey, different colours can be present and are often beautifully spread out.  Patterns may resemble trees, shrubs, plants, clouds, rivers and even animals.

He goes on to say "the ancients" organised agates into different types.  Each one was given a name that highlighted its difference from the 'common agate'.  That could be colour, markings or texture.dendritic agate stones Red agate was known as haemachates.  The prefix 'haema' coming from the Greek for 'blood' with reference to the stone's colour.  The name 'achates' came from a river in Sicily where the stone was first discovered.

Regarding the discovery of agate Theophrastus wrote; these stones have been "found to exist in almost every nation on Earth."  Those with patterns resembling trees and shrubs were called dendrachates (from dendrite) whilst other types were "idly named" according to the powers they held or because of their similarity to animal skin. 

The Ancient Roman author, naturalist and natural philosopher Pliny the Elder [23 AD - 79 AD] also wrote about the properties and meaning of agate in his works "Naturalis Historia".  He frequently referenced the work of Theophrastus.

Pliny states;

"Achates was a stone formerly in high esteem, but now held in none. It was first found in Sicily, near a river of that name; but has since been discovered in numerous other localities. In size it exceeds any other stones of this class, and the varieties of it are numerous, the name varying accordingly."

He goes on to name several types of agate stone and explains where it can be found.  Like Theophrastus he also makes reference to dendrachates (dendritic agate) which he says is "marked with small shrubs".

He talks about the meaning of different types of agate from India and their distinctive markings.  He says "the sight of some is beneficial for the eyes whilst others when held in the mouth allay thirst.  Then there are those which are good for counteracting the effects of poison inflicted by the scorpion.  Agate stone can also be found in Cyprus."

He believed those with uniform colour would render athletes invincible and said agate with the highest value has the transparency of glass.

oval shaped crazy lace agate stone

What is Agate?

Agate is a translucent variety of chalcedony made up almost entirely of silicon dioxide.  Stones are often black, white or grey but can also be exceptionally colourful.  Any colour and banding that's present comes from impurities of other minerals.

Quartz crystals in agate are colourless in their purest form.  With the presence of iron they turn red or brown, with manganese they turn pink and with chromium a shade of green.

The easiest agate stone to identify usually has clear distinct bands.  Some argue that to be classified as a 'true' agate the stone must exhibit banding.  There are several types however that are not banded.

Over the years there have been endless discussions regarding the use of trade names.  From a geological perspective they can often be inaccurate and misleading.

Moss and dendritic agate don't exhibit visible banding but feature inclusions known as dendrites. Often mistaken for organic matter, dendrites are crystal formations similar to those seen on glass during winter.  They're caused primarily by impurities of iron and manganese.

The word 'dendrite' comes from Greek for 'tree' and refers to a 'branching form'.  Stones with dendritic inclusions can sometimes mistaken for fossils.

dendritic inclusions in a beige coloured opaque piece of rock

Although frequently found within igneous rocks, agate can also occur in other rock types as well.  Its formation which is exceptionally complex begins when ground water containing silica (sand or quartz) that has entered the rock through holes, dries up leaving behind a residue of minerals.

As the process repeats, multiple layers of minerals build up within the rock following the outline of the cavity.  Once full the mass begins to crystallise.  Quartz crystals often grow in any space left unfilled.  When their tips point towards a void, the structure is known as a geode.

The cavity containing the crystallised minerals is known as a nodule.  Depending on the type of rock it can be incredibly resilient to weathering.  It's not unusual for the nodule to survive long after the host rock has eroded. The agate formation remains locked away until the nodule is found and broken open.

On Mohs scale of mineral hardness agate grades 7.  Being relatively hard makes it much easier to work with.

large agate stones on display in a museum display cabinet

Natural Agate Types

Natural agate tends to be characterised by concentric, curved or angular banding.  Stones can also exhibit other curious and intricate patterns.  Hundreds of different types of agate can be found around the world and many have been given trade names.  These often indicate the locality where the stone is found or a particular colour or characteristic.

Fortification agate is a generic name for stones whose bands are arranged at sharp angles.  The name stems from the shape which was once believed to resemble the lines of a fortress.  A fortification is a defensive wall or other reinforcement built to strengthen a building against attack.

Blue lace and crazy lace are both types of fortification agate.

Botswana agate comes from Botswana, Brazil agate from Brazil, fire agate exhibits a distinctive flash of colour caused by inclusions of hematite.  Polka dot agate often but not always is spotted.

Agatized dinosaur bone despite the name is not a natural agate at all.  The word 'agatized' is often but not always used as a prefix because it describes a process that has taken place.

colourful agate stone with distinctive banding. In a museum display cabinet

More Facts About Agate

An agate was believed to have been the second stone in the third row of the high priest breastplate.  This religious garment from biblical times was adorned with twelve gemstones.  It was worn by the Jewish high priest whilst presenting himself to God.

Agate is dependant on the presence of other minerals for its colour.  Black, white and grey stones are often dyed to make them more appealing to the wider commercial market.

The practice of dying rocks and minerals can be traced back thousands of years. Agate has long been known to be porous with the ability to hold dyes particularly well.

Despite everything that has been learnt about the formation of agate so much is still not fully understood.  The formation of this stone has never been studied from start to finish in real time.  Nor has it been possible to recreate agate in a laboratory setting.  For this reason much of what is known is supposition.

Agate Healing Properties

Agate is a grounding stone that brings the emotional, physical and mental into balance.  Being grounded means we're well connected with the earth.  That helps us remain calm, rational and make better decisions especially when surrounded by chaos.

The healing properties of agate are soothing and calming and harmonize both positive and negative energies.  It works at its own pace but is powerful yet gentle. Agate is associated with stamina, vitality and strength.

Crystals may be used to bring information to the surface that's deeply rooted in the subconscious.  They can also be used to rebuild self-confidence.
Ideal for enhancing concentration, agate can improve analytical ability and help find practical solutions to difficult problems.  Its energies promote inspiration, creativity and improve motivation.  It encourages the truth to be spoken and helps deal with negativity and bitterness especially in relation to love.

Agate is associated with the star sign of gemini.  According to the traditional and ayurvedic birthstone chart it's the birthstone for May.  On the mystical birthstone chart agate is the birthstone for September.

Article Pictures

Picture 1, 3 (crazy lace agate) and 4 (dendritic inclusions in agate) and the last picture in our article are courtesy of Stan Celestian.  Three of the stones are on display in the Natural History Museum Los Angeles. 

The second picture of dendritic agate is courtesy of Steve (Singingstone48 - Flickr). 

The agate stones in the museum display cabinet are in the Smithsonian Museum of Natural History Washington D.C.  Photo by Stone Mania.  Most of the pictures are clickable and redirect to the original non-compressed photo. 

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