The agate rock is a type of translucent microcrystalline quartz formation of chalcedony formed primarily by tremendous volcanic activity over millions of years.
The sheer quality of agate is due to the continuous deposition of silicate minerals as it is being formed underground or above-ground, with the help of both superheated water (with crystals) and lava flow. Agate is usually found the crevices of igneous rock formations; they are typically seen as nubs between rocks or as part of a host rock.
Identifying agate correctly is crucial if you want to be able to find and purchase the real thing. There are simulants and synthetics in the market that may make it confusing for first-time buyers to identify genuine agate from the fakes. Agate is popular because of its parallel and concentric bands.
These bands differ in color because of slight changes to the chemical composition of the mineralization inside the agate gems. With agate, you can expect a wild ride when it comes to coloration.
There are deep reds that are comparable to the reds of rubies, for example, as well as deep and light bands of blue. Colors from different areas of the color spectrum can occur in a single sample of agate quickly, because of how these semiprecious stones form over millions of years.
Agates are sought after by gem collectors and enthusiasts because they look amazing once cut and polished, and they can be purchased almost anywhere.
Unlike sapphire or ruby, buying agate will not break the bank. You can build your first collection of gems by focusing on lower-cost stones like agate, a type of silicate chalcedony that occurs in multiple intricate patterns and colors. Here are some methods of checking if the gem you are holding is agate or not.
This is a truly simple method of weeding out a fake gem – if you have access to a genuine one. If the stone is unpolished, you may have to crack open the specimen to see the insides. Gemologists will often point out the parallel or concentric banding patterns on agate rocks.
The bans are often multicolored (involving two or more colors), and they all grow from a center. A sample of agate (especially the large ones) may show elaborate patterns and multiple “centers” where the bands of color form. Take note that a few other minerals like jasper have the same internal characteristics as agate, so if you have an agate sample, take a closer look at the layering of color to find out which is which. If the patterns are similar, then you are holding a genuine sample of agate.
Density Hand Test
If you want to check the density of an agate stone, you need to compare its weight with another stone (even natural stone or pebble). The reason this test is at least partially accurate is that agate is denser than it looks, and it displaces more water despite its scale.
A real agate rock might look small, but it will be more substantial than a stone of a different type that might be slightly bigger than the sample that you have. A more scientific approach is to calculate the actual density of the gem you are testing. Agate displaces water at a rate of 2.64 g/cm3.
If the agate sample you have is split and you have access to the core of the gem, feel free to rub the crystal with your fingertips gently. Genuine agate will have an almost waxy feel to it, depending on the striations of the banding.
Others say that it has a smooth feel, but all in all, the texture shouldn’t be super soft, there should be some resistance to it, but not so much that you can’t glide your fingertips across the core of the gem. If you feel anything else, it’s probably a fake agate or another crystal or mineral altogether.
Genuine agate feels warm on the hands during wintertime and remains relatively calm during the summer. Simulants and fakes will readily take on the ambient temperature of the environment. If the room is warm, a simulant will be warm, and during winter, the simulant will be chilly.
Visual Test One: Transparency
This is one of the more definitive tests for agate. If you have a more massive rock in your possession, you may have to crack it open so you can access the stone’s core. This applies only to people who may have agate that is still embedded in a piece of the host rock. For those who have a cut and polished gem, there is no need to split open the treasure anymore.
Get a bright flashlight, preferably one that provides more than a few lumens of light when you turn it on. Position the torch a few inches away from the edge of the rock to be examined and turn it on.
If you have genuine agate, you should see the light from the flashlight diffract, and some of the light should be able to pass through the rock with minimum effort. If none of the light makes it through, the sample is not transparent, and you should be suspicious if you’re holding an agate or not.
When light passes through the agate, you should also notice that some of the color bands inside will become brighter and clearer. In case there is more opacity than transparency, the sample you are holding is either a synthetic or natural simulant of agate. If it is a natural simulant, the closes crystal to agate in terms of appearance is jasper.
Visual Test Two: Over Text
This method tests the level of transparency of the rock sample you are examining. Since agate is transparent, if you position agate above a text, for example, you should still be able to read the book, albeit with minor difficulty.
Any blurring is normal, but the text underneath the sample should remain fairly readable or at least recognizable. By recognizable, we mean that you should be able to make out the text on the paper.