"Fire
agate is a very beautiful,
often mysterious and misunderstood stone..."
...as most pulidors will
tell you.
C U T T I N G & P O L I S H I N G F A Q
We sell some of the best quality fire agate rough available on the internet, all of our material is handpicked for us by our minero amigo. Using his advise and 15 years of knowledge, along with our expertise on the web - together we formulate the value and decide the rarity of every fire agate we sell. In return, we share all profits with him and his family in Calvillo.
Once
in awhile we experience problems with newcomers to the fire
agate cutting and
polishing world, and sometimes they are disappointed
with their finished product or don't physically see any fire in the
rough they purchase. Because they do not have the expertise in how
the layers of color are formulated or the true hardness of the stone
- this knowledge is very hard
to come by for any lapidarist, because as a general rule the miners
don't share their secrets.
Below
are some tips about fire agate rough, and in the
future we hope to continually add information here to help our
clients to get the most out of their quality
fire agate rough purchases from us here in México.
Click here
for cutting and polishing helpful tips and techniques.
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Agate cracked
in half to reveal the fire found hidden within. |
Visual layers
of limonite which refract light into fire. |
If
you do not see any visual fire, this does not mean that there is
no fire in the
rough material. Sometimes a specimen needs to be cracked in half (photo
above left) to find the fire (photo left), or
if you see lines (layers) in
a sideview - this is the limonita, which is the refracted material that
creates the illusion
of fire (photo above middle).
We do not sell the mine floor sweepings you see at great discounts on eBay, we only sell good to excellent quality material, for amatuer and professional lapidarists alike. Because of our commitment to our miners, we do not accept returns for any rough material sold. We know you will get at least double your money back (minimum) from your rough purchases, but it is also possible to make 10 times the value of your original investment as well, on our high grade rough - depending on your lapidary skills and patience.
As new veins of fire agate in the rock are found, prices and quality can fluctuate - sometimes the miners will not give us their very best rough material because they know that they can make alot more money by polishing it and selling the cabochons themselves. But when there is a new strike, we can usually get them to part with a few kilos of their high grade rough for us.
Sometimes
you find quartz-like inclusions growing inside
of a fire agate raw specimens. The
sprays of needles are inclusions of sagenite. These multicolored sprays
are highly prized and sought after rare specimen by collectors,
and not found in all fire agates. On
average we only come across a couple fire agate rough with inclusions
per every 25 or 30 kilos
of material we receive from the Calvillo mines - as uncommon
(but not as rare) as 'lluvia negra', black rain fire agate.
'LOS
MINEROS' MEMORIAL
ROUGH AGATE FAQ
 Solid black agate rough specimen from the Negrita mine. |
|
Sometimes your material may look like it has a black coating (photo above) with no visible fire, these specimens are from the 'Negrita' mine high up in the Sierra Mountains, with entrance only accessible by climbing up a sheer cliff. Known for some amazing gems, the agate from the 'Negrita' mine is a black agate and offset by the fire to make a striking gem. (see photos below)
Mined in 2004
Mined in 2006
WE WILL CONTINUE TO ADD TO THIS FAQ
AS LONG AS NEW QUESTIONS ARISE...
FIRE
AGATE CUTTING & POLISHING INFORMATION
Inside Every Fire Agate Is A Hidden Treasure...
Unfortunately
alot of stones are destroyed by cutters who are
unfamiliar with the nature
and formation of Fire Agate.
Always
Look For The Hidden Potential,
The
Treasure Is Waiting For You...
Fire Agate can be intimidating to the professional and amateur cutter alike. Fire agate ranging in color from clear to dark brown and the layers of the iron oxide minerals limonite or goethite that interact with white light to create the "fire" or iridescence. There is usually a milky translucent chalcedony that marks the stone's top. The characteristics of rough fire agate can vary considerably, depending on the mine and source material.
Fire agate
is deposited in botryoidal form, meaning the structure resembles bunches
of grapes,
commonly called 'bubbles' or 'bubbly'. Most
pieces of fire agate rough are twisted
and deposited in a variety of angles. This creates a challenge
for gem cutters because the sought after color layers follow highly
irregular contours in the underlying brown agate. The art of cutting
fire agate lies in finding the brightest, best-colored layer
and following its contours wherever they lead and not cut through the
iridescent layer itself. Sometimes a slip in cutting reveals an
even better color
layer, but more often, the stone is completely ruined. With
one light pass of a diamond grinder you can lose an entire layer of fire,
so patience is a must. 
The
'bubbles' in fire agate vary tremendously in size, from almost microscopic
to single large
bubbles that can be in the 15mm range or larger, and in some rare cases,
a lot larger. Generally speaking, the kind of rough displaying larger "bubbles" is
best suited for cutting on standard lapidary equipment, because these
shapes are
easier to work on flat grinding and sanding surfaces. Fire agate with
intricately contoured, irregular or 'bubbly' color can only
adequately be shaped using gem carving techniques. Standard lapidary
equipment
is suitable for cutting most types of fire agate, be careful and take
the time to carefully study how each stone is laid out by mother
nature.Most lapidarists
prefer to cut directly from rough specimens, but occasionally excellent
window polished material is available at reasonable prices. Naturally
you pay a premium for someone else's knowledge and labor in doing
the main work for you. Most window polished specimens
often don't make good material to cut
through, and only small stones can be cut from what remains of the pre-polished
window.The gemmy
layers vary in thickness, with the brightest and best layer often
at the point between the chalcedony and
the brown agate material. Sometimes these layers are only a 1000th
of an inch thick, and they are best cut by leaving a slight
amount
of clear chalcedony over the top as protection if possible. If you
sand right down to the color layer, there is a good chance that sanding
and polishing can
destroy it. In better quality
rough, the color layers are arranged successively so that cutting through
one
layer reveals another. Or there may be
multiple bands of layers ranging from very thin to reasonably thick.
The gamble is deciding which is the brightest and most desirable color
layer and to make it the top of your stone. Color layers usually
run in succession from bronze to gold to red and then green, with the
rarer blues and purple colors to follow (if they exist). With some multicolor
agate there is a 2nd layer of even stronger colors, but it is a gamble
to venture past the original layers of fire in hopes of a second more
colorful layer.
C U T T I N G
Wet
and inspect your rough under magnification in bright sunlight. Look
it over as closely as possible. If you can see through the chalcedony, try
to find flashes that indicate color layers. Don't be disappointed if you
don't see any color, it may still be there but you'll have to work harder
to get to it. Next, carefully examine the edges of the brown agate
at various angles in the light, searching for layers or flashes of color.
Some rough comes without the chalcedony "cap", so it's easier to evaluate. But usually the first step in cutting is to eliminate the chalcedony. If it's thick, some careful trim-sawing can save a lot of grinding. But never cut into the dark agate layer! Removing this "cap" is hard work, tough on equipment and sometimes fruitless: lots of good looking rough turns out to be your basic garden rock. But there's no way to tell for sure until enough of the cap material has been reduced to allow any colors from underneath to be seen. Direct sunshine makes it possible to do some very accurate grinding; indoor lighting, including quartz halogen floodlights, despite their intensity usually lie about the location and brightness of color planes within the rough. Being able to really see what you're doing is the single most important factor in cutting this stone.
It's the nature of most fire agate cabs to require some contouring to follow the color layers, and flat grinding wheels are designed to cut convex or flat surfaces. One of the toughest jobs is to grind into the chalcedony crevices and valleys between the larger individual bubbles areas. Unless you decide to invest in specialized diamond wheels shaped for this job, the only way I know to do it is to use the edge of the grinding wheel. Begin grinding one hillside first, then change to the other edge of the wheel to do the opposite one. You'll discover that, with care, the face of the wheel does all the work and the edge gets very little wear.
How most miners work around this problem...
CAUTION: This type of cutting can be very dangerous as well. The wheel can grab the piece of rough (and your fingers). Work very cautiously, bearing in mind also that putting pressure on the edges of most standard diamond wheels can quickly ruin the wheel. Work carefully, and never use excessive pressure.
When grinding has proceeded
far enough that vague brown shapes can be seen through the chalcedony,
iridescence should be visible as well.
Grind a little, sand and inspect carefully
in good light sunlight. Repeat until the desired fire
colors are fully revealed. The
color
layers are thicker on top of the bubbles and thin down on the slopes
and edges, so do most of your initial sanding on the top.
YOUR FIRE AGATE TELLS YOU HOW IT SHOULD BE CUT
Don't try to force
it into any particular shape - if you are uncomfortable with anything
but symmetrical shapes
or intend to cut only calibrated sizes for standard mountings, you
may find fire agate very frustrating. It doesn't adapt easily
to this style of cutting unless you don't mind wasting alot of color
and being satisfied with what some call "brown-edges" or "deadspots";
a pool of shimmering fire surrounded by an ugly dead area of plain
brown agate. Sometimes this style of cutting is unavoidable, but if you
let
the patch of bright color define the edges of the finished stone, you
will end up with a much more pleasing and higher value stone.
Have the patience to stick with the sanding. There is no feeling more exciting than having a boring bronze stone suddenly start showing amazing colors of green, purple and blue, mixed together with reds, yellows and oranges.
Sometimes you win, but more often you lose... if you have reason to suspect that multiple or brighter color layers could be present in the underlying layers it is well worth the gamble. You usually end up with more boring or golden stones than you ever wanted anyway, so sometimes it is better to try for the the reds and greens and purples!
F R E E H A N D I N G
This
technique is used by our 'pulidor' and many of the old
timers as well - they don't believe in dop sticks and rarely use
foredom style grinders. Use
the same light touch
that you would use on opal, allowing you to remove only the smallest
amount of material at a time, so that you don't grind through a fire
layer.
Some people have asked why our stones look so good and they cannot reproduce this quality with the rough they purchase from us. You have to get rid of those machines and polish your agates by hand. Our miners start off using 150 or 180 grit paper and finish with 2500 to 3000 grit and a polishing powder. Use lots of water and only working in bright sunlight so you can work the layers to their optimum. Most miners don't even belive in using dop sticks, they want to always feel the stone in their hands, it gives them more control.
© 2011 Mexico Gemstones
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