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Strata Gem January 2003
President’s Message
The month of December is just about over. We had a great Christmas party in Stansbury at the Oquirrh Mills Restaurant. It was really nice, great friends and great food. I would like to thank Ruth, Ardith and Larry for there work putting the party together. Everything turned out really nice. I would like to wish everyone a happy and safe New Year.
Looking forward to seeing all our Snowbirds in January. I would like to thank everyone again for all their help and support without it we would not have such a great club.
Whatever else changes through the years, the glory of the holidays remains to brighten all hearts with its radiant beauty. May the light shine upon your pathway and bless you with joy and happiness through out the New Year, and always enjoy life's journey.
Donna M. Chavez President
Members News
Club Calendar: · Jan. 14 Monthly Meeting 7:30 PM. · Feb. 11 Monthly Meeting 7:30 PM. · Mar. 11 Monthly Meeting 7:30 PM. · April Fieldtrip Honey Onyx · Apr. 8 Monthly Meeting 7:30 PM. Snowbirds welcome back. · May Fieldtrip Last Chance Agate · May 13 Monthly Meeting 7:30 PM. · June Fieldtrip Geodes · June Date Pending Grab Bag Fill/Meeting 9:00 AM. at Jay's House. · No Meeting In July · July or Aug. Fieldtrip Vernon Wonder Stone · Aug. Date Pending Monthly Meeting Held In Conjunction With Annual Crafts Day & Steak Fry. Location: Pavilion in Settlement Canyon. · Sep. 9 Monthly Meeting 7:30 PM. · Sep. 27-29 Our Annual Gem & Mineral Show · Oct. 14 Monthly Meeting 7:30 PM. · Nov. 11 Monthly Meeting 7:30 PM. · Dec. Christmas Party, (date pending).
Vice Prez Mess & Letter From The Editor: We had a great Christmas Party down here in Quartzsite. Our numbers were a little smaller this year because it was a little later this year & some of our members had already gone home for Christmas. But it was a real good time for those that attended.
While I’m away it would really help if our group would help keep me informed on what is going on up there, so I can get it in the paper. You can always leave me a message at 1-877-386-1941 any time day & nigh, and there won’t be a long distant charge for you. Just a reminder, I need everything about 1 ½ to 2 weeks before the end of the month so I can get everything in the mail ASAP.
Dennis Chapman Editor & VP The Peridot Asteroid By Dr. William S. Cordua
One of the most exotic gemstones is from outer space — the rare meteorites called pallasites. These are flashy mixtures of translucent green to yellow olivine (peridot) found as large crystals in a matrix of iron-nickel alloy. When cut and polished the contrast between the olivine and metal is startlingly beautiful. No wonder they are so pricey.
The first pallasite was described in 1772 by Pyotr Pallas. It was a 1,600 pound mass that fell in Siberia. Pallasite is also known in quantity from Kiowa County, Kansas, from the Imilac pallasite that fell in the desert of Chile and the Salta Pallasite of Argentina.
How do such meteorites form and where do they come from? Such a mixture of silicates as olivine and metal are presumed to be found in the earth along the core-mantle boundary. How could rocks from the core of a planet get into outer space?
Modern models of asteroid and planet formation suggest asteroids perhaps 50-200 km in diameter may form a layering similar to that of the earth. The accumulation of that much material, including heat producing radioactive substances, would cause the body to melt and the denser iron and other metals to sink to the center of the body. The less dense silicates such as olivine would not sink so deeply, and, with other minerals, form the outer layers of the asteroid. This is also what happens in a blast furnace, when the melted rock separates into the denser iron and lighter materials that will cool to slag. Thus some larger asteroids have the equivalent to the crust, mantle, and core of the earth.
In the earth, though, the outer core is still molten because our planet is so much larger and still has abundant heat-producing radioactive materials in its interior. The asteroids, on the other hand, would have completely cooled and crystallized. Along their core-mantle boundaries, the separation of the silicates and metals would not be perfect — what natural process ever goes perfectly? Perhaps some late pulse forced cooling iron up into the mush of olivine crystals. Thus the pallasite is born.
The next step is getting the materials out of an asteroid and to earth. Here we use the fact that asteroids, over the length of geologic time, have tended to collide violently with each other. A big enough collision between two asteroids will fracture both sending pieces flying. These fragmented planetoids are the source of meteorites, including pallasites. Those unfortunate enough to be pulled in by the earth’s gravity, after a journey for millennia in space, will fall as meteorites. Since only a tiny part of an asteroid will be a core-mantle boundary, pallasites should be scarce, and they are.
Some asteroid collisions may not be quite so destructive, it is possible that a less violent collision may strip away most of an asteroid’s mantle, leaving an olivine studded metallic mass — an asteroid whose surface is covered with peridot gemstones. That would be quite a find.
How could we find such an asteroid, out of the millions stretched through billions of kilometers of space? It’s not as impossible as it seems. The mixture of olivine and metal would give off a distinctive spectrum that can be detected with sensitive instruments on earth or in satellites. Some known asteroids do give spectral data showing olivine at the surface. These are termed A-type asteroids, such as 246 Asporia. Some are 30 to 65 km in diameter. It is astonishing to think that some may be peridot encrusted. Of curse other large asteroids may have pallasite layers within if they escaped a collision large enough to blast them to splinters. Then the pallasite “ore” would have to be recovered by interplanetary “hard rock” mining.
So as prospectors were drawn west by visions of “El Dorado” or the “Mother Lode,” perhaps future space explorers will blast of in search of the peridot asteroid.
From Leaveilie News via THE GLACIAL DRIFTER 5&6/02 Via T-Town Rockhound 8/02 The More They Stay The Same By Kevin Dermody
A fabulous fossil is found and becomes a sensation. A man with claims to the property where the fossil was found declares the fossil is his and wins it by legal means. He then proceeds to use the find for his own benefit. Meanwhile, the discoverer of the fossil loses in court and is forced to pay money. Government troops confiscate the fossil, which eventually makes its way into respectable scientific establishment for proper study.
I'm talking about the story of Sue, the tyrannosaur, right?
Wrong! I'm talking about the first recognized giant reptile fossil discovered seven decades before Richard Owen first coined the word, "dinosaur." In 1770 or 1780 a pair of immense jaws was discovered in an underground chalk quarry near Maestricht, Netherlands. The quarry was already well known to collectors for the many shellfish fossils found there, but these jaws were something else! One collector for the Teyler Museum in Haarlem, Dr. C.K. Hoffmann, generously paid the quarry workers to remove the jaws intact. He then took it home and summoned Pieter and Adrien Camper, father and son Dutch anatomists, to examine the find. Adrien Camper declared, correctly, that the jaws were of an unknown type of giant marine reptile.
News of the fossil find reached the clergyman Canon Godin, who owned the lands directly above the quarry. Proclaiming the fossil was his under feudal law, Godin sued Hoffmann for ownership and, backed up by other clergymen, won his case in court. Hoffmann had to give up the find that he had already paid for, and to pay the court expenses as well. Godin then built a chapel near his estate and put the jaws in a glass shrine for all the world to see.
Eventually, the world did more than just see. By 1795 the French Revolution was in full swing. The army of the French Republic had defeated the army of Austria and was about to bombard Maestricht and the nearby fortress of St. Peters Mountain. The reputation of the fossil jaws had spread far and wide by this time, however, and General Pichegru, commander of the French army, gave orders that Godin's chapel, which was near the fort was to be spared. The grateful Godin used the opportunity to hide his treasure within the town. When Maestricht surrendered, and the disappearance of the jaws was discovered, Pichegru offered a reward of 600 bottles of fine wine to anyone who could find the lost bones. Soon several grenadiers returned from town with their booty to claim the prize.
The jaws were taken to the Jardin des Plantes in Paris, where they would be examined by Baron Georges Cuvier, France's leading anatomist. Cuvier came to the conclusion that Adrien Camper was right - the jaws were of a giant marine reptile. This study verified two points. One was that organisms can become completely extinct naturally without any help from Man. Many extinct plants and animals seemed to become extinct even before Man existed. Cuvier had already demonstrated this by his examination of fossil elephants. The uniqueness of the Dutch find brought up the second point, that the lower, and presumably older rock strata held fossils of animals that were less and less like the animals that live today, including reptiles of a form and size unlike any known today. In 1822, a decade before the first bones of what would be recognized as those of dinosaurs were discovered, the animal was named masasaurus, the lizard of the Meuse River, where Maestricht was situated. Masasaurs would be recognized as lizards, no dinosaurs, that were the last marine reptiles to arise before the extinctions at the end of the Mesozoic Era.
Today fossils are being found world-wide at an enormous rate, giving new insights into how life existed in the past, and how those past worlds compare with our own. There is also a vast commerce in these same fossils, many legal, some illegal, and a few that are perfectly legal but still seem unjust. As they say, "The more things change..."
Bell, Gorden L., Jr. 1997. Introduction to Mosasauridae. Jack M. Callaway and Elizabeth L. Nichols (eds.), Ancient Marine Reptiles pp. 281-292. Academic Press (San Diego, London, Boston, New York, Sydney, Tokyo, Toronto) Desmond, Adrian J, 197.5. The Hot-Blooded Dinosaurs. A Revolution in Paleontology. The Dial Press/James Wade. 238pp.
From Rock Buster News 02/98 via Stoney Statements, 8/02. Via THE RockCollector 9/02
Words Of Wisdom: Learn from the mistakes of others, you can’t live long enough to make them all yourself.
From Golden Spike News 3/2001 The Glacial Drifter 11/01 Meriwether Lewis’ Near Fatal Rockhound Experience By Brenda Hankins. AFMS Lewis & Clark Chairperson
The summer of 1804 found the Lewis and Clark Expedition traveling west against the current of the Missouri River. At present day Kansas City, in the great River bend, the Corps of Discovery turned north toward the Mandan Villages. What lay ahead came to be described as a passage through the Garden of Eden and a summer filled with incredible experiences.
Lewis saw and described the coyote which was new to science. He found an area of the River that was 70 yards wide and three miles long that was completely covered with white feathers, deposited by a flock of birds preening on a sandbar up the River. Private Joseph Fields killed the Expedition’s first buffalo, whose hump became the favored food second only to the beaver’s tail.
On the Fourth of July, the men of the Expedition became the first American citizens to celebrate the nation’s birthday west of the Mississippi River, The day started with the firing of the cannon and ended with the enjoyment of a second dram of whiskey. In honor of the nation’s 18th birthday, Lewis and Clark named a creek “Independence”. Today, in present day Atchison, Kansas, you can stand in the bedroom where Amelia Earhart was born and look out the second story window into the Missouri River and almost see the National park marker commemorating the Expedition’s 1804 Fourth of July celebration.
Another incredible experience that summer almost ended the Lewis and Clark Expedition as we know it. The Expedition came close to losing its primary namesake and its only designated rockhound. Meriwether Lewis almost met his demise in a situation that continues to haunt some modern day rockhounds.
Lewis was known to be more knowledgeable in botany than in mineralogy, but he took all his responsibilities seriously. On August 22, about 650 miles up the Missouri River, past the mouth of the Platt River, Lewis found and studied a substance that he believed to be arsenic or cobalt. According to Clark’s journal, Lewis attempted to taste and smell the specimen so that he could conclusively record what it was. Lewis was immediately overcome by the substance and was nearly poisoned. To ease his condition, Lewis took some of Rush’s Pills, often called “Thunderbolts” because of their impact on the bowels! Without a doubt, the pills were not the appropriate treatment strategy and only added to Lewis’ misery. Fortunately, however, Lewis survived his near fatal rockhound experience.
Reference: Ambrose, Stephen. Undaunted Courage: Meriwether Lewis, Thomas Jefferson, and the Opening of the American West. 1997. New York: Touchtone.
From AFMS Newsletter March 02 Via Gneiss Times 4/02
Tip:
Coat the inside of abalone shell with Vaseline and then brush diluted hydrochloric acid over the outside of the shell - one part hydrochloric acid and six parts water. Be sure to add the acid to the water, not the other way around. After most of the coating has been eaten away, wash with plenty of water. The shell can be cut with an ordinary hacksaw and a rough file. The final sanding can be done on 700 grit wet sandpaper. Always grind abalone wet - the dust is toxic. For polishing, use Tripoli on a loose cloth buff, followed by light buffing with rouge on a loose cloth buff. Work wet; never let abalone get hot.
From Australian Lap. Journal via The Nugget, 8/02. Via THE RockCollector 9/02
Great Predictions By Experts
“I think there is a world market for maybe five computers.” — Thomas Watson, chairman of IBM, 1943
“We don’t like their sound, and guitar music is on the way out.” — Decca Recording Co. rejecting the Beatles, 1962.
from GOLDEN SPIKE NEWS 3/2001 via The Glacial Drifter 11/01
Rockhound Jargon For Beginners
Here's a brief list of abbreviations and unusual jargon commonly used by collectors. Mm - Micromount, a specimen requiring magnification that its in a 3/4" box, also called a micro. Macro - Somewhere between a micro and a TN, not quite either. tn/TN - Thumbnail, a specimen that fits in a 1 1/4 box - Also known as a Perky box, about the size of your thumb nail toenail somewhere btw a TN and a miniature. Min - Miniature, a specimen around 2". Scab - Small cabinet sized specimen, 3-4". Cab - Cabinet sized specimen, 4" and larger. Doorstop - Anything really big and preferably ugly. Rabbit - What you've picked up when the fieldtrip Rock - leader looks at it and says "Throw it at that rabbit over there!". Leaverite - Same as above, you guessed it, leaverite there. Xl, xx, xtal - Crystal xln, xtl crystalline xls crystals. MR - Mineralogical Record, the best magazine available for the collector. EM - The Encyclopedia of Minerals, a handy reference book. HBM - The Handbook of Mineralogy, another great reference tool. Fleischer (aka Glossary) - The Glossary of Mineral Species, essential list of all known species, updated every 4 yrs, by Fleischer/Mandarino. MSH - Mont St. Hilaire, famous mineral locality. Cab Cabochon, a stone cut in a low dome and polished. Sleeper - A very underpriced specimen, these are the most fun to buy, but they are fairly rare, mostly sold by dealers that know less than their customers. Keystone - Half price, on specimens sold wholesale from one dealer to another (specimens occasionally doubled in price and then marked as being keystoned). UV - Ultraviolet. SW - Short wave ultraviolet. LW - Long wave ultraviolet. REE - Rare earth elements, aka rare earths, neat elements like lanthanum and yttrium, found in neat minerals like monazite and bastnaesite.
Author: Tim Jokela Jr Via the Slate on the internet Via THE RockCollector 9/02
Gem Show Calendar
If you know of any events coming up, PLEASE let me know as soon as possible. If anything is wrong PLEASE let me know as soon as possible.
Feb 22-23 Idaho Gem Club Show, Western Idaho Fairgrounds, Glenwood & State Street, Boise, ID.
Mar 1-2 Owyhee Gem & Mineral Society Show, O'Connor Fieldhouse, 2200 Blaine, Caldwell, ID.
Mar 7-9 Golden Spike Club Show, Union Station, 25th and Wall, Ogden, UT.
Mar 8-9 Magic Valley Gem Club Show, National Fuard Armory, Friontier Rd. (just east of CST), Twin Falls, ID.
Apr 26-27 Logan Rock Club Show, Logan Rec. Center, 195 S. 100th, Logan UT.
May 10-11 Santa Cruz Mineral & Gem Society Show, Corner of Center and Church Streets, Reno, NV.
July 11-13 RMFMS Show and Convention, hosted by the Natrona County Rockhounds Club, Parkway Plaza Hotel and Convention Center, Casper, WY.
Aug 8-10 Annual Contin-tail Rock Swap and Show, Rodeo Grounds, Buena Vista, CO.
Sep. 26-28 Tooele Gem & Mineral Show, Tooele County Fair Complex, 400 West 200 North, Tooele, UT.
Where Did Christopher Columbus Go Wrong? by Erston Barnhart
Columbus has been described as a man who didn’t know where he was going, didn’t know where he had been, did it several more times, and all on borrowed money. However, he is the only foreigner honored with a legal holiday in the United States - unless you live in some parts of California where you are asked to observe “Indigenous Americans Day” instead.
The idea that the world is round was widely accepted by the time of Columbus. The main dissent was from the church, which held that the earth was a flat disc covered with a canopy, probably to provide a physical manifestation of heaven.
The spherical earth theory was proposed by several Greeks, the first of which was Aristotle (384-322 BC), who observed the shadow on the moon during an eclipse and concluded that this could only be caused by a round object.
The first who actually sought to prove this theory was Eratosthenes (circa 276-196 BC). Born in Libya, he was the chief of the library at Alexandria, Egypt. This library was the repository of more than 100,000 scrolls containing the world’s collective knowledge.
Eratosthenes heard of a well in what is now Aswan where the sun’s reflection could be seen in the water of the well on June 21st, the longest day of the year. He surmised, that the sun was directly above the earth at that moment. He knew that this location was directly south of Alexandria and by measuring the shadow of an obelisk in Alexandria at the same time there was no shadow at the well, he computed the length of two sides of a triangle, the length of the shadow and the height of the obelisk. He figured the angle of the triangle, which was 7-12’, approximately equal to one fiftieth of a circle’s 3600.
He still needed one more measurement. The Greek standard of measurement was the stadia (based on the size of a Greek race course). Standard camel performance was to cover 100 stadia per day, and since it took a camel 50 days to make the trip between his two points, he calculated the distance to be 5000 stadia, multiplied by 50 and come up with a figure of 250,000 stadia for the earth’s circumference. Translated to modern measurements, his earth measured 25,000 miles, amazingly close to the actual distance at the poles of 24,860 miles. His scientific apparatus for this experiment consisted of something to measure the length of a shadow.
Unfortunately, some people cannot leave well enough alone. Sometime later, another Greek scholar named Strabo, for some unknown reason, reduced Eratoshenes’ figure from 25,000 to 18,000 miles. By Columbus’ time the original calculation had been overlooked and it was this latter figure that Columbus relied on for his voyage.
Columbus knew the approximate distance from Europe to Japan, west to east, thanks to Marco Polo’s journeys to the Far East. If his calculations of the earth’s circumference of 18,000 miles jad been correct, he would probably have been justified in assuming he had reached the Orient. A Greek scholar, 1700 years before Columbus’ voyage had it right, and if Columbus had had the correct information, he may have realized he was 7,000 miles short of his objective.
Reference: Don’t Know Much About Geography by Kenneth C. Davis
from Rock Buster News, 3/01 via AFNS Newsletter April 2001 The Glacial Drifter 10/01
Finding And Finishing Ammonites By Dave Daigle, Edmonton, Alberta, Canada rokhound@planet.eon.net
Collecting Ammonites: Somewhere in the Lower Middle Devonian, some group of Nautiloids gave rise to a modest group of coiled Cephalopods, the Ammonites. They really picked up their pace in the Mesozoic Period and became more plentiful and varied, and were dispersed almost worldwide. They differed somewhat from their modern day cousins, mainly by internal structure.
As they died on the ocean floor, they were buried in the sea mud. In North America that mud became, for the purpose of this paper, either shale or Ironstone. Normally the mud would be pressed into flat layers of shale by the pressure of the sea and mud above it, but the hard bodies kept their shape and became concretions. Those concretions, or roundish UFO shaped nodules of shale and Ironstone, are found in the Aragonite Zones of the Badlands, in Southern Saskatchewan, Southern and Mid Alberta, and Northern Montana and are the geologic structures where Ammonites are found today. You usually find concretions in the upper sides of banks on existing rivers, such as the Bow River, or in the Badlands banks, which were rivers at one time. Surface collecting is easiest, although some rockhounds have adapted a type of long tined pitchfork for prodding down into the soft Bentonite beds in hope of striking a concretion.
Once found, the trick is to break open the concretion. If cleaned off carefully, one can usually see small fracture lines or, sometimes, a piece of the Ammonite peeking through a spot at the edge of the nodule. A sharp chisel, a hammer, and a steady hand, and most concretions will break in half where the Ammonite is laying usually exposing a concave side of the concretion with shell attached and the Ammonite itself imbedded in the other half. If you are after the Gem…or shell … then you can break the Ammonite out of the now halved concretion. But, if you want a complete Ammonite, if indeed it is complete, than traditional methods of removing a fossil from matrix are used. (Thank goodness for Foredoms and Dremels.)
Trivia time….The Ammonites got their name from the chief God of the Triad of Thebes Amun, who was often depicted as a Ram with curved horns.
The area covered by the Bearspaw Sea, which included Northern Montana, Alberta and Western Saskatchewan is where we find most of the Placenticeras Meeki species. The Meeki is, in my humble opinion, the best gem quality shell. These concretions with, hopefully, Mekki inside them, can be anywhere from 6" to 3" in diameter! The bigger ones, and most others, are "halved" right on the spot to see what treasures they hold and to more easily get them back to your transport. Most will fit into a backpack but some we have to "sling" and carry these on our backs also. Heavy? …..You Bet!
But alas, sometimes you find the other kind, what we call barren shale, and your efforts of digging them out and breaking them in half are not rewarded.
Hmmm, heavy …. Reminds me of a time when I was loaded down with a heavy pack full of Ammonite, walking on a game trail at the bottom of a coulee on the way back to my truck. I came around a corner, with my head down .. of course, (typical Rock hounding syndrome) and came face to face with a huge Whitetail Buck! Now, it's nice to see nature from a distance, but up close those bucks are huge!!! He startled me and I fell backwards on my pack and watched as the buck took off straight up the side of the coulee like the hounds of hell were chasing it. I recall, as I laid there looking up, that the bank was about 100 feet high and pretty well straight up! Well, after kicking my legs for a while, and laughing at my predicament of looking, for all the world, just like a turtle flipped on it's back with it's legs wiggling, and rocking my body I finally rolled on my side and managed to get back on my feet. To this day, I still don't know which one of us were scared more, the buck or me.
Do you still want to go hunting for these concretions with that beautiful Ammonite shell inside? A word of warning, you must, at least in Canada, have the appropriate Ammonite permit to collect Ammonites! The fine can be severe for collecting without one. But it doesn't stop with a license, once you have returned home with your treasures, you must then fill out a disposition form and take pictures of your finds, which are sent off to the Tyrell Museum, where the experts look things over. If you have not discovered a new species or anything of paleontological value, they send you a reply…and then the Ammonites are yours.
From Raw To Gem Ammonite I will attempt, in my humble way, to describe to you the way in which I work Ammonite. Please bear with me, as writing is not my forte'.
Once I have gotten my Ammonites home, It's time to clean them to see shat I've got. This can involve anything from muriatic acid baths…remember AAA, always add acid…never water to acid, to a simple cleaning with a brush and water. Some Ammonite has a thin film of white, or unformed calcite on top of the gem, this is when acid is used in dilute amounts to clean it off. If it's too filmy it usually extends down through the shell and makes it rather useless for gem quality pieces. Although with acid, the colors are still there.
Next comes the decision to keep it whole. If indeed you found a whole one in one piece, you should keep it as such …. Or to "gem it", if it's in many fractured pieces. If it's whole, it's sanded by hand later. I've found no better way to do it, although I've experimented plenty.
Ammonites, it seems, always start their lives with dark colored, blue and green shells. Probably to aid them in hiding from their many predators. Their shell is in layers, starting from red, to the oranges and yellows and then to the greens and blues of the last layers. So, if you feel brave, you can continue to sand down through the layers to get at the rare greens and blues. But, like an opal, be careful, after the last blue color….there's nothing but shale and you will have lost your color!
But alas, I wander off….Back to it then. There is much to do before laying on the sandpaper. Firstly, if not whole, you must cut away the excess shale, this can be a tricky process also. You should try and keep about 1/2 of shale still attached to the Ammonite Gem. Remember, the Ammonite is a Nautiloid and shaped accordingly, abeit flattened out somewhat from the pressures of time. Therefore there will be gem on "both sides" of the Ammonite, and you have to decide where to cut it. Flat spots are preferred, but they are rare in a Nautiloid shaped body.
Depending upon the color of the shale you probably have to seal the Ammonite. If whole, then you seal the whole Ammonite. But for this paper, let's assume that you have Ammonite pieces. The reason for sealing the Ammonite is to darken the shale down and to seal the gem shell to the shale beneath it. Again, referring to opal, the darker the matrix, such as Black Mintabe Opal, the brighter the color or fire is seen. Same thing with Ammonite gem. The darker the shale below, the brighter the colors of the gem will seem to be.
Sometimes, Ammonites come with the shell sitting loosely on the shale cores. This is where the Optican Sealer comes in. You need to heat the Ammonite pieces up to about 150 degrees and then apply the sealer to the gem with a brush. I use sheets of 1/2 inch steel and lay them across the burner elements of a kitchen range. But if you're doing a single piece, or just a few, a slow oven will do just nicely. The warm stone will actually draw the sealer down through the gem and into the shale beneath it, thus effectively sealing the gem to the shale and making the shale darker. Take the pieces off the heat and let them sit for a few days. The sealer never quite seems to harden, but almost.
Now, the pieces have to be cut into fairly flat pieces or freeforms. Not too small yet as you have to use the lap wheels next. I guess this part just takes practice, but you can actually find some fairly flat pieces on the Ammonite … you just have to picture flat enough places and sizes to eventually make gems from. Sometimes your pieces are small. But they are flat.
The Gem Quality of the pieces are important and could alter your decision for gem or freeform pieces. "A" grade or better have a finely fractured texture with either a multitude of colors or a single brilliant color. The grades differ to c, b, a, aa and triple a grades. Now that we have formed the AFAC we hope that the grades can be regulated. But for now beware, some peoples ideas of A grade are not always the same as someone else's. Some gem has wide fracture lines and poorer colors and are therefore of lesser quality. After you have done it for a while, you can tell this when you first crack open the concretion.
Next comes the flat laps. I usually start with about a 400 grit … carefully … the gem is not that hard. Think of it as a regular shell and you'll be fine. All you want to do in this stage is to "flatten" the piece you are working on. Some of it, of course, can never be flattened and I believe these pieces would be great for intarsia work, but since I haven't got that figured out yet, for freeform pieces. Once you have your piece fairly flat, look at the center of the piece, you'll probably and … if you stopped soon enough .. that it's the green or blue color. If you didn't stop soon enough, then you'll find shale,…Damn! And you start over with a flatter piece. Seriously though, keep an eye on it and you'll be fine. This is the stage where you must decide, freeform or gem quality. If you are doing gems instead of freeform, you cut out your gems before you start your 600 stage. The most popular way to cut gems … which also gives you the least waste … is the rock bandsaw. But, the traditional saw if fine, just lan your gems out carefully as to waste as little of it as possible …. It's expensive stuff! An oval of 10x14 can be $80.00 or more if it's "AA" or better!
I dop my gems with a two part 5 minute epoxy on to welding rod pieces. Just warm up the metal rods with a torch slightly and stick it to the already placed epoxy on the back of the gem (the shale). I round them into calibrated shapes with a 400 or 600 grit expandable wheel with sc grit.
Finally, the gem must be capped. Some lappers use glass, some use a product such as Envirotex .. a two part sealer/glue that hardens rock solid. These methods are ok, but for rings and high abuse jewelry you still can't beat Spinel or Quartz caps. I use tempered glass or I make my own caps from quartz, for brooches and most of my freeforms.
I hope I have been able to shed some light on the long kept secrets of Ammonite Gems. But if we are going to sell rough, people need to know how to work it properly. It is too precious and beautiful a gem for people to have to learn the hard way, as I did.
Copyright 1997-1998. This document may be copied and used in mineral and gem club newsletters without asking permission, given that the article is reprinted in total and that credit is given the author and Lapidary Digest as the source.
From The British Columbia Rockhounder, Vol. 3 # 1, and Gem & Mineral Federation of Canada, Vol. 20, # 1
Via RMFMS Newsletter 2/01
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