The situation with Fire Agate has been reminiscent of what happened with the first finds of black opal at Lightning Ridge. The stones were so different that it was a while before the stone was accepted. Most gemmologist and geologists were puzzled the first time they saw Fire Agate.
Fire Agate has been found to be indigenous to the South West USA and Central and Northern Mexico. The first recorded discovery seems to be at the end of 1945 at Wiley Well also known as Coon Hollow in South eastern California near the Arizona border. This may not be the first discovery as many prospectors and rocks hounds are secretive about disclosing their source.
Sometime in the 1960's it was discovered in Mexico. I first saw Fire Agate in Mexico in 1973, but it was not until the late 1970's that I saw fine quality stones. At this time the mines at Deer Creek, Arizona and the Mexican mines in the state of Aguascalientes began to produce stunning fine quality material. There was much interest and demand for these stones. This was not to be for long almost simultaneously disaster struck at the Deer Creek mines and at the Mexican mines there was severe drainage problems. The mines became ponds for much of the year and there were mud slides and collapsing in of the mines. Some of the Mexican mines were up to 100 feet deep.
It must be understood that the mines in Mexico and Deer Creek Arizona were in very isolated mountainous areas often just a trail into the mountains. It was a problem, and often impossible to get in heavy earth moving equipment to remove the top soil or over burden to expose the Agate bearing basalt and Rhyolite country rock. It is also not easy to extract the Fire Agate from pockets and seams in the country rock.
FORMATION OF FIRE AGATE
Fire Agate is a rare form of Chalcedony. It is hydrothermally formed when rising hot water, saturated with colloidal silica and iron oxide, enters seams crevices and pockets in the country rock. As this solution cooled, the Silica formed Chalcedony often in botryoidal form on any surface available. As the solution lost Silica, too much iron oxide remained in suspension to re-stablise this. The iron oxide formed extremely thin layers of goethite or limonite crystals upon the Chalcedony. This cycle kept repeating, thus forming Chalcedony with extremely thin layers of iron crystals. These are known as Schiller layers. Latest research indicates when light passes through them it causes the interference colour in Fire Agate. It is the same chemical formula as any other type of quartz S1-O2.
CUTTING FIRE AGATE
Rough uncut Fire Agate is usually a dull brownish rock often in botryoidal form, showing no play of colour. It is the skilful work of the lapiderist that brings out the iridescent rainbow play of colour in this unique gemstone. It does present an unusual challenge to the Lapiderist. The secret is understanding how the layered structure and botryoidal form have to be taken account when cutting this stone. The process is a reversal of the growth pattern. The difficulty is in finding the contour of the fine layers, and the orientation of the stone. First carefully study the stone to determine the structure and orientation of the fire layers. This is best done when the stone is wet and in bright sun light. In the UK a bright light will probably have to do. The fire bearing layers are often under a Chalcedony cap which needs to be removed by sawing or rough grinding to just above the darker coloured fire layers.
The next step is the critical part on a wet 220 grit grinding wheel, or one can use a well worn 100 sanding drum and carefully follow the contour of the fire layers. Always use lots of water, patience, a light touch, and frequent checking when the stone is wet under a good light, is necessary. Remember the fire lay are extremely thin. They can be thinner than paper. If there are dips in the stone when using a sanding drum instead of having the sanding belt evenly with an outer edge of the drum. Pull it about 3-8th of an inch past the edge. In this way it is good for contour sanding and getting into the dips in the stone. The Mexicans use a flexible sanding disc. This way they can bend it into the dips in the stone. Again a light hand and use lots of water and constant checking under a good light. Most American material is usually more botryoidical and bubble like in its formation. Fortunately, most Mexican material is more flat and sheet like. Also most has been windowed as soon as it comes from the mine. A saw cut or rough ground to expose the fire layers. It is simply a case of shaping up the stone - fine sanding and polishing. A lot of Mexican fire agate is multi layered so carefully check the stone wet and under good light. Possibly there is better colour under the exposed colour. This is often a gamble. The first colour layer is usually orange followed by red through the colour spectrum to violet. On multi layered Mexican stones I would not advise sanding through the red green layers as the purple violet colours are usually not strong in Mexican Fire Agate.
PRESENT DAY INFORMATION
Some mining is taking place in the state of Aguascalientes in the Sierra mountains around the tiny pueblo of El Terrero. They usually lack heavy earth moving equipment and production is sporadic. The mines are still are having drainage problems. Only last year there was mud slides and flooding at the major mines. It is possible that most of the high grade fire agate was depleted in the late 1970's.
The main producer in the USA is Deer Creek, Arizona on the slopes of the Galiuros mountains in Graham County. Dave Penny and his partner Sarah Scholz are commercially mining with heavy equipment(backhoe and bulldozers etc). They are pretty much a two person operation. They are producing some stunning material though it is not coming cheap. They are mining in the area of the old claims of Warren Hughes and Don Van Dusen(the early pioneers in the mining of Fire Agate). Another area commercially producing Fire Agate is on Apache a native American reservation some 40 miles north of Deer Creek. Only Native American Apache are allowed to mine and no heavy machinery is allowed so it has limited production near the surface as they are only using hand tools.
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