Agate Gemstone Information

Introduction

We know agate has been used by man for at least 3000 years as it got its name from the Ancient Greek philosopher Theophrastus.

Theophrastus named the gemstone after the Achates River in Sicily where he came across them. The island was a Greek colony before it was conquered by the Romans and was the source of agate gemstones for many centuries. Agate was used to make rings, seals and ornaments and is a variety of chalcedony which in turn is a type of quartz.

Chalcedony has many varieties including onyx, jasper and bloodstone but agate is generally the banded or striped version although with these often similar quartzes they can be easily confused. Agates are made up of successive layers of material, sometimes curved, sometime flat, of various thickness, color and transparency.

The variety of colors and patterns has led to a number of different names for agate including lace agate, moss agate and fire agate. As a rule, agate has a striped appearance with green, yellow, red and brown being the most common color schemes but some dyed versions are evenly colored throughout.

Agates come in a wide variety of natural colors, brown, red, lilac, pink, yellow as well as black, gray and white but as it is quite a porous gemstone it does take dye quite well so come brightly colored or even colored gems may well have been treated in this way.

With colored gemstones it is usually the color that really determines the price but with agates things are a little different. As a rule natural blues and greens are rarer than other colors in agates so they tend to fetch the higher prices but the most expensive gemstones, Fire Agates, have a dark body with a rainbow of iridescent color on display.

Moss Agate is mostly creamy colored with greenish inclusions that look like moss, plants or grass while Dentritic Agate, sometimes called Tree Agate, is similar but the inclusions are more brown and branch-like.

The blue agates can be the most expensive with the very rare Ellensburg Agates reaching top prices and Blue Lace and Cellmark Agates also being well valued. Other agates tend to come in a variety of colors in different patterns and it is the combination of bright colors in interesting patterns that raises the price of these gemstones.

Agate is a banded form of chalcedony and comes in a variety of patterns and colors.

Some of these patterns and colors are similar and common enough to be collected together and referred to as a distinct type of agate.

A chalcedony is usually referred to as an agate if it shows any of the following properties:

• banding caused by different colors or different arrangement of the layers
• translucency with being multicolored
• translucency with a nodular shape and colored inclusions

It is a gemstone that has been used throughout the ages in many locations and has such a variety of appearances that it has gained many names.

Fortification Agate

Fortification Agate is the most common and recognizable form with concentric lines which follow the outline of the cavity in which they were formed. It got its name because it is supposed to look like the plans of a fort.

Water-line Agate

Water-line Agate is also named for the pattern of the rock, water lay within the cavity before draining away leaving a straight band of silica. This was repeated over a long period of time leaving layer upon layer and creating a succession of parallel lines.

Onyx

Onyx is a well known type of usually black and white agate (a water-line agate) although it also appears in other colors.

Sardonyx

Sardonyx is another version of agate similar to onyx with parallel banding but with red and white coloring (sometimes red, black and white).

Crazy Lace Agate

Crazy Lace Agate is white or creamy based agate with swirls of red or brown

Moss Agate

Moss Agate is not so much banded but decorated with green inclusions which resemble moss, trees or leaves.

Iris Agate

Iris Agate is not named because it looks like a human eye but because it displays many colors in very delicate banding.

Thunder Egg Agates

Thunder Egg Agates are a baseball sized spheres which are plain and bumpy on the outside but inside have colored and layered crystals. They are cut in two or sliced to display the knobby exterior and the beautiful interior.

Agate Geodes

Agate Geodes are similar to Thunder Eggs but whereas Thunder eggs are usually solid, the geodes are mostly hollow.

Dendritic Agate

Dendritic Agate is one of the most valuable form of agate and is near colorless or pale-colored with black or brown tree- or fern-like inclusions.

Fire Agate

Fire Agate is another of the most expensive varieties. It is found in the western parts of North America and displays iridescent coloring quite like that of opal.

These are just a few of the more well-known agates but there are many more out there, possibly hundreds, many named after their style of decoration, Ring Agate, Plume Agate, Ribbon Agate and so on.

Usually when discussing clarity in gemstones such as sapphires or aquamarines we discuss how clear the stone appears to the naked eye, how cloudiness or inclusions can impact on the value of a stone but with agates we have a slightly different approach. With a very few exceptions, agates can be described as translucent, that is it allows light to pass through it as opposed to opaque which does not allow any light through.

We have mentioned already that agate is a type of Chalcedony and being a chalcedony gemstone is determined by two things – the size of its crystals and its mineral composition. Agate shares the same crystal size and mineral composition but differs from other forms of chalcedony (jasper for example) by its translucent or semitransparent form. This is called diaphaneity – how easily light passes through a material.

Chakras are the energy centers in your body also referred to as Qi or Prana. There are seven Chakras throughout the body each influencing a particular physical, emotional or mental state.

The seven chakras are as follows, Crown, Third Eye, Throat, Heart, Solar Plexus, Sacred and Root. The word Chakra is a Sanskrit word meaning wheel. Each chakra is assigned a color of influence and a gemstone which has a particularly dominant color will be connected with that color’s chakra point.

Sometimes in life our Chakras become unbalanced or blocked and need to be realigned or cleansed. One way to do this is through the use of Chakra healing stones. These stones or crystals are colored to correspond to individual chakras, red for the Root Chakra, orange for the Sacred, yellow for the Solar Plexus, green for the Heart, blue for the Throat, Indigo for the Third Eye and purple for the Crown Chakra. So we can see that Blue Lace Agate with its predominantly blue color would be most beneficial for the Throat Chakra, Moss Agate for the Heart Chakra, Fire Agate is a flexible gemstone which could affect any Chakra according to its main color although orange and red for the Sacred and Root Chakra is most common.

Without going into too much detail the Crown Chakra is your connection to the divine or your spiritual guide and is located at the top of your head. The Third Eye Chakra is your intuition or aspirations and is on your forehead between your eyes. Next, comes the Throat Chakra which deals with our ability to communicate and no prizes for knowing where that one is. The fourth Chakra is the Heart Chakra, concerned as you might imagine with matters of love and happiness, this one is found in the center of your chest above your heart. The Solar Plexus Chakra is placed at the upper abdomen area and is associated with confidence and self control. The Sacred Chakra to do with sexuality and pleasure is just below the belly button or navel and finally the Root Chakra deals with career, money and attachment and is located at the base of our spine.

When pricing colored gemstones we need to consider what is known as the 4 Cs, color, clarity, cut and carat and usually it is the color that is the most important. The 4Cs should always be your guide when buying any colored gemstone but agate has a few special exceptions to these golden rules.

Color in combination with pattern sets the price with agates although of course size does matter – if you have two equally interesting and colorful gemstones the bigger one will get a better price. Cut does not really come into it other than the gem should be cut and polished to show off its interesting markings to the maximum.

Certain types of agate can get higher prices but it is generally a moderately price gemstone. Fire agates with a good display of iridescent color get good prices, Moss and Dendritic Agates can get high values with particularly interesting inclusions especially ones that seem to display a whole landscape of trees, fields, bushes and lakes. Other specimens can have shells trapped within the stone or may be formed within the branches of ancient trees which may have become fossilized or petrified over the millennia.

The source of the agate does not usually affect the price with one or two exceptions. Ellensburg Blue Agate is only found in Washington State on the west coast of America where a combination of 43 different minerals have created a special blue agate which can claim very high prices for a well cut and polished gemstone.

Agate has been used as a gemstone for as long as man has made jewelry and in antiquity is was quite highly valued. It was the first gemstone ever written down in an ancient document and at least 3500 years ago Egyptians procured colorful agates from the Achates River on the Mediterranean island of Sicily (from which the modern name ‘agate’ comes from). Consequently the tombs of ancient Egyptian royalty are littered with agate ornaments and jewelry.

Not far from Sicily is the Greek island of Crete where archaeological digs in Knossos have discovered agate carvings dating back to the Bronze Age. People in Idar-Oberstein in Germany have been cutting and polishing locally mined agates for well over 500 years and documents suggest mining has been undertaken there for around 3000 years. It was here that the first cases of high quality dyed agates were discovered, although dyeing agate has been going on for thousands of years it was not to such a high standard. When the local mines were exhausted, German immigrants in Brazil found huge resources of plain white agate which was sent back to Germany to be dyed to continue a very profitable industry.

As the world was opened up to new explorers more and more types of agate were discovered, Blue Lace Agate is an attractive gemstone. This agate was first discovered in the early 1960’s by George Swanson, in the southwestern African region of the Kalahari Desert of Namibia and was soon a darling of the gem world. Botswana Agate is a beautiful white and purple or peach striped agate discovered in this southern African country while Fire Agate is only found in the western parts of North America and was discovered as recently as the 1950s.

Most agates are formed within ancient volcanic lava or igneous rocks. Hot molten rock rises to the surface crust of the earth and begins to cool. Within the soft, warm lava gas bubbles form as well as cracks and cavities where lava flows overlapped or cooled at different rates. The lava hardens into rock and the gasses escape leaving little pockets of space. Into these pockets fluids such as silica, rich in dissolved quartz molecules, flowed and settled. Over time these fluids form crystals which are influenced by changes in pressure, temperature and other mineral impurities which can enter the cavity creating the colors and patterns so loved in agate.

When the agate quartz has fully formed it is generally harder than the surrounding rock and wind, rain and ice slowly erodes away everything but the hard agates. These agates then get washed away by streams and creeks and sit on river beds waiting to be collected by alluvial miners millions of years later.

Since Agate usually forms in cooling lava rock it is found in all the significant areas of the world where volcanic activity has taken place, generally where the earth’s continental plates meet and in mountain ranges.

Agate can be found throughout the world, either mined from alluvial deposits near rivers and oceans or mined from the earth’s depths with the biggest modern day deposits being found in Brazil and Uruguay. Particular varieties of agate are found in different parts of the world. Fire agate is found on the western states and in Mexico on the North American continent. Moss Agate is discovered in India, Brazil and Uruguay, Dentritic Agate is found in Australia, Brazil, China. Madagascar and Namibia, Blue Lace Agate comes from southern Africa and Crazy Lace Agate comes from Chihuahua in northern Mexico.

Agate is generally untreated as it is not a particularly expensive colored gemstone so expensive heat treatments are not very common but dyeing agate does happen in order to enhance some of the colors and the banding.

Some ordinary colored agate can be colored with a variety of chemical solutions to produce much more colorful gemstones. Agate is a porous gem so the dye can really penetrate into the body of the crystal and make permanent and distinctive changes.

The Idar-Oberstein mines of Germany were a source of excellent gemstones for thousands of years and the gem cutters of that region perfected the polishing technique using a water powered sandstone wheel on an axis in the 15th century. Unfortunately the local mines were depleted by the 19th century so agates had to be imported. German emigrants to Brazil discovered huge deposits of agate in their new country but it was a dull gray color however gem cutters back home in Germany discovered a method of turning these humdrum stones into something more beautiful.

To turn an agate red the gray gemstones were first boiled in a strong bicarbonate solution. Meanwhile iron nails were soaked in nitric acid until they had dissolved, then the boiled agate was soaked in the iron nitrate solution for a month before being slowly heated and slowly cooled to produce red agate or carnelian.

Similar methods were used to make Blue Agate and Green Agate using chrome, nickel, potassium and cyanide and these days honey and sulfuric acid creates a brown agate while hydrochloric acid and make a yellow gemstone.

These are age old processes and not necessarily untoward unless the information is hidden or misrepresented in some way. Of course, we at GemSelect will disclose any form of enhancement or treatment.

Agate is a gorgeous gemstone with a stunning array of colors and some wonderful patterns, so varied that one type or another will surely take your fancy. It has a Mohs hardness rating of about 7 so it is durable enough to be worn as just about any piece of jewelry although rings should perhaps be in a protective setting.
To learn more about the Mohs hardness scale please read our article here

Agates can appear in very large sizes and in interesting shapes so make for great one-off designs for pendants or brooches. Oval or round cabochon-cut gemstones are very popular as are fancy cut designs. Look out for some very interesting moss or dentritic agates that almost seemed to be designed or drawn they so resemble a landscape or forest.

The biggest Agate weighs 60,000 kilos

The largest and heaviest agate found so far weighs over 60 thousand kilograms. This enormous gemstone is 2.70 meters high, 5 meters across and nearly 5 meters thick. It was discovered in China in 2009 and made the Guinness Book of World Records.

Agate and Jasper can combine in one gemstone

Agates are a translucent chalcedony, Jasper is an opaque chalcedony. Sometimes these two rocks form together. Combine an agate and a jasper and what have you got? A Jaspagate!

Agate was intricately carved 3000 years ago

An agate seal was unearthed in Pylos, western Greece dated to 1450 BC and called the Pylos Combat Agate was so detailed that experts believe it could only be carved using a magnifying glass – even though no such glass existed in Ancient Greece!

Mithradates, the king of Pontus and ‘the scourge of Rome’ had a treasure of three thousand bowls made of agate rock.

Agate is the mystical birthstone for September and the zodiac birthstone for Gemini.

Agate is a wedding anniversary gemstone and an alternative

Agate is an alternative 12th wedding anniversary gemstone, Moss Agate is an alternative for the 14th wedding anniversary, Onyx is the 7th wedding anniversary gemstone and Carnelian is the 17th wedding anniversary gemstone.

Agate can be cleaned very easily using warm soapy water and a soft brush. Keeping in mind that agate is quartz and its hardness and durability, be sure to not use any other objects that are harder than agate for scrubbing or cleaning. As with most gemstones, you should not use any household chemicals when caring or cleaning your agate gemstone or gemstone jewelry pieces. Agate should avoid any prolonged exposure to extreme of heat as it may cause permanent damage to the gemstone. When storing agate, it should be stored inside a fabric-lined box or wrapped in a soft cloth. Agate should be kept away from other gemstones and jewelry to ensure unnecessary damage or scratching from other harder gemstones.

Obviously buying gemstones from a reputable dealer is the best approach but this is not always possible when you are out searching for a great gemstone or a bargain!

Agate is not a very expensive gemstone so are not often the victim of counterfeit or fake efforts but some unscrupulous dealers may try to pass off a worthless object as an agate. Despite this the relative affordability means it is hardly worth the expense of an appraisal so a few handy tips in identifying an agate would be useful.

First of all, Agate is a strong durable gemstone so it will not scratch easily with a knife or a nail. It will also scratch a piece of common glass so that could be a quick test.

Second is color. Agates come in a variety of colors and patterns and each have their own properties but anything that has a too bright or neon color is at least dyed if not fake. Dyeing is fine so long as you know what you are getting. Agate is a banded gemstone so being all one color is also a sign of being dyed or not an agate at all.

If you are able to hold the agate then it should feel quite substantial, agate is a dense stone so should feel quite heavy. It is also a slow conductor of heat so will not warm up quickly in your hand but remain quite cool (unless it is a particularly warm day).

This is not a complete guide on how to spot a fake gemstone but I hope it helps.

At GemSelect, we stand by our gemstones as being as we describe them, any treatments are disclosed and our return policy means you can feel quite assured when ordering from us.

Agates are an archaic gemstone, used by man since the dawn of time, from Bronze Age, and possibly Stone Age, tribe people to Ancient Greeks, Persians and Egyptians, by owning one you are continuing this line of history.

The lovely colors and unique patterns mean each stone is unlike another, they may share common traits and distinctive styles among the varieties but each agate is a one-of-a-kind.

Even though this gemstone seems so exotic and unusual it is very affordable and appeals to jewelry lovers and collectors alike and its reputation as a stone of health and balance is unparalleled.

Some gemstones show a distinct or dramatic change in color under different light sources. Look at a garnet under electric or artificial light and it could look red, take it outside into the sunlight and all of a sudden it is green! This remarkable effect only occurs in a few gemstones, Alexandrite, Garnet and some Sapphires being the most well known but does NOT occur in agates.