Agate - Common Stone Uncommon Beauty

Agates are primarily composed of silica or silicon dioxide, the same material that makes up sand that occurs across the globe. Silica is known to be the single most abundant mineral on the planet, and since agates are mostly silica, it stands to reason that these stones can be found on all five continents and on dozens of countries. Millions of years ago, water flowing on the surface of the earth and through crevices in rocks dissolved silica. This solution then collected in cavities within the rock formation. As the water evaporated away, salt deposits were left behind. The salts were deposited in layers of varying thickness, each layer containing secondary minerals or impurities (besides by primary mineral silica) which influenced the color of the layer. The presence of chromium in the solution caused the layer to be green in color. Copper salts on the other hand gave the layer a blue color, and iron compounds resulted in colors ranging from burnt orange to brown. In geologic time (millions to tens of millions of years) and under intense heat and pressure, the salts became petrified and formed stones as we see them today. Although agates were formed at multiple locations under a wide variety of conditions, the common factors that were required to develop agates were a source of silica-rich volcanic ash, groundwater or surface runoff that could dissolve the silica, and secondary minerals that were responsible for the colored layers of the stone.



Agates are often used in fashion jewelry where the goal is to create pieces that are beautiful and trendy and yet affordable. The demand for agates can generally be attributed to two primary reasons, both of which relate to the abundance with which this stone occurs in nature. Firstly, because of the way in which these stones formed over a wide range of conditions, the patterns and colors that occur in nature are virtually limitless. So there is always a fairly steady supply of agates in a variety of colors and patterns to suite virtually any jewelry application. Secondly, since agates are found in great abundance, they are relatively inexpensive, which makes them ideally suited for fashion jewelry.



In the world of fashion jewelry, there are a few varieties of agates that deserve special mention. At the top of that list are Botswana agates. These stones are known for their bright colors and interesting banded patterns. Botswana agates are usually cut in cabochon form, polished to a high sheen and set in sterling silver settings to make some truly stunning silver pendants. A noteworthy variety of agates are fire agates. These stones can range in color from bright flaming orange to a more subdued brownish orange. The colors are due to the iron content of the stone. Fire agates are found predominantly in Mexico, although some minor finds have been identified in parts of Central America as well. Cyclops agates have an interesting natural pattern. These agates are formed by deposition of alternate layers of black (or nearly black) and off white to white silica. The stones are cut to expose concentric circles that resemble a single eye; hence the name. Finally, petrified wood deserves mention as being one of the more unusual forms of agates.


As the stone was being formed millions of years ago, the silica solution entrapped materials like wood, leaves and other organic matter. With time, this organic matter decomposed and was replaced by minerals of different colors. Today, petrified wood has the visual appearance of the organic matter, but has the physical characteristics of rock. Cut and polished properly, petrified wood can be used to make interesting beads for fashion jewelry.