1408 GIBBINS ROAD, ARLINGTON, TEXAS 76011Volume 69, Issue 04, April 2014
ROCKHOUND NEWS OF THE ARLINGTON GEM MINERAL CLUB
Rock of the Month
Fire Agate
ISSUE
4
5 / How to Cut Fire Agate
Rare Diamond
7
8 / April Fools Day Recipe
Bench Tips
9
9 / May InterGem Show
Annual AGMC Show
10 / April Class Report
11 / April Class Schedule
12 / May Tentative Class Schedule
13 / Lapidary Calendar
14 / Programs
14 / Lapidary Shop Talk
15
16 / Area Gem & Mineral Shows
March Minutes
How To Cut And Polish Fire Agate
Nova Wells, cc
Fire agate has the same properties common to all agates, plus some special conditions. It is a chalcedony and is formed in botryoidal layers, which means ‘like a bunch of grapes.’ The ‘fire’ comes from very thin layers of iron oxide that coat occasional layers of clear chalcedony, with other clear and brown layers in between. Fire agate is predominately brown in color but often has masses of white attached. Good fire agate will have more than one layer of ‘fire,’ or iron oxide which produces iridescence in the same way a skim of oil produces color on water. There are places in both New Mexico and Arizona where the stone may be collected and it is also mined in Mexico.
Begin by using the saw to remove any amount of plain white stone that is attached. Be careful to check each saw cut to be sure you didn’t cut into some color (fire). If there is no layer of fire visible begin to grind carefully over the surface of the stone until you can spot one or more layers of iridescence. Fire agate sold by dealers will often have a ‘window’ cut to show where the color is.
Because it is botryoidal most fire agate must be worked by hand because it involves concave as well as convex surfaces. There are two types of tools you can use with equal success to work fire agate. You can use a Dremel or Flex Shaft with a series of diamond tools or you can use short pieces of wood dowel in several sizes that you shape yourself. The dowel can be put in an electric drill and used with commercial diamond powder in grades from grind to polish.
The trick is to locate the layer of iridescence covering as much surface as possible and then remove all but the thinnest layer of clear chalcedony that covers it. I begin with small round or pointed diamond bits in the Dremel to remove unwanted stone. USE LOTS OF WATER WHEN GRINDING. Because you are working close to your eyes (and nose) and producing powdered stone, it would be very easy to inhale the dust causing permanent damage to your lungs if you allow any dryness to occur. Never mind the possibility of cracking the stone. Stones are replaceable—your lungs aren’t.
The next series of steps is to use diamond-imbedded Dremel tools graded from 180 grit to 15,000 grit. There are two types of tools you can use with equal success to work fire agate. Mine are ‘Nova Points’ but there are probably other brands that are just as good. Getting the stone smooth and showing the iridescence in a finished state may take several hours. Final polish can be done with a felt wheel and tin oxide. The rewards are worth the patience required.
Rare Diamond Reveals Earth's Interior is All Wet
By Becky Oskin, Senior Writer March 12, 2014 2:14 PM
A diamond from Juína, Brazil, containing a water-rich inclusion of the olivine mineral ringwoodite.
Credit: Richard Siemens/University of Alberta
A battered diamond that survived a trip from "hell" confirms a long-held theory: Earth's mantle holds an ocean's worth of water. "It's actually the confirmation that there is a very, very large amount of water that's trapped in a really distinct layer in the deep Earth," said Graham Pearson, lead study author and a geochemist at the University of Alberta in Canada. The findings were published today (March 12) in the journal Nature. The worthless-looking diamond encloses a tiny piece of an olivine mineral called ringwoodite, and it's the first time the mineral has been found on Earth's surface in anything other than meteorites or laboratories. Ringwoodite only forms under extreme pressure, such as the crushing load about 320 miles (515 kilometers) deep in the mantle.
What's in the mantle?
Most of Earth's volume is mantle, the hot rock layer between the crust and the core. Too deep to drill, the mantle's composition is a mystery leavened by two clues: meteorites, and hunks of rock heaved up by volcanoes. First, scientists think the composition of the Earth's mantle is similar to that of meteorites called chondrites, which are chiefly made of olivine. Second, lava belched by volcanoes sometimes taps the mantle, bringing up chunks of odd minerals that hint at the intense heat and pressure olivine endures in the bowels of the Earth. In recent decades, researchers have also recreated mantle settings in laboratories, zapping olivine with lasers, shooting minerals with massive guns and squeezing rocks between diamond anvils to mimic the Earth's interior.
These laboratory studies suggest that olivine morphs into a variety of forms corresponding to the depth at which it is found. The new forms of crystal accommodate the increasing pressures. Changes in the speed of earthquake waves also support this model. Seismic waves suddenly speed up or slow down at certain depths in the mantle. Researcher think these speed zones arise from olivine's changing configurations. For example, 323 to 410 miles (520 to 660 km) deep, between two sharp speed breaks, olivine is thought to become ringwoodite. But until now, no one had direct evidence that olivine was actually ringwoodite at this depth. "Most people (including me) never expected to see such a sample. Samples from the transition zone and lower mantle are exceedingly rare and are only found in a few, unusual diamonds," Hans Keppler, a geochemist at the University of Bayreuth in Germany, wrote in a commentary also published in Nature today.
Earth's deepest ocean
The diamond from Brazil confirms that the models are correct: Olivine is ringwoodite at this depth, a layer called the mantle transition zone. And it resolves a long-running debate about water in the mantle transition zone. The ringwoodite is 1.5 percent water, present not as a liquid but as hydroxide ions (oxygen and hydrogen atoms bound together). The results suggest there could be a vast store of water in the mantle transition zone, which stretches from 254 to 410 miles (410 to 660 km) deep."It translates into a very, very large mass of water, approaching the sort of mass of water that's present in all the world's ocean," Pearson told Live Science's Our Amazing Planet.
Plate tectonics recycles Earth's crust by pushing and pulling slabs of oceanic crust into subduction zones, where it sinks into the mantle. This crust, soaked by the ocean, ferries water into the mantle. Many of these slabs end up stuck in the mantle transition zone. "We think that a significant portion of the water in the mantle transition zone is from the emplacement of these slabs," Pearson said. "The transition zone seems to be a graveyard of subducted slabs."
Keppler noted that it's possible the volcanic eruption that brought the deep diamond to Earth's surface may have sampled an unusually water-rich part of the mantle, and that not all of the transition-zone layer may be as wet as indicated by the ringwoodite. "If the source of the magma is an unusual mantle reservoir, there is the possibility that, at other places in the transition zone, ringwoodite contains less water than the sample found by Pearson and colleagues," Keppler wrote. "However, in light of this sample, models with anhydrous, or water-poor, transition zones seem rather unlikely."
Ride on a rocket
A violent volcanic eruption called a kimberlite quickly carried this particular diamond from deep in the mantle. "The eruption of a kimberlite is analogous to dropping a Mentos mint into a bottle of soda," Pearson said. "It's a very energetic, gas-charged reaction that blasts its way to Earth's surface."
The tiny, green crystal, scarred from its 325-mile (525 km) trip to the surface, was bought from diamond miners in Juína, Brazil. The mine's ultradeep diamonds are misshapen and beaten up by their long journey. "They literally look like they've been to hell and back," Pearson said. The diamonds are usually discarded because they carry no commercial value, he said, but for geoscientists, the gems provide a rare peek into Earth's innards.
The ringwoodite discovery was accidental, as Pearson and his co-authors were actually searching for a means of dating the diamonds. The researchers think careful sample preparation is the key to finding more ringwoodite, because heating ultradeep diamonds, as happens when scientists polish crystals for analysis, causes the olivine to change shape. "We think it's possible ringwoodite may have been found by other researchers before, but the way they prepared their samples caused it to change back to a lower-pressure form," Pearson said.
Email Becky Oskinor follow her @beckyoskin. Follow us@OAPlanet, Facebookand Google+. Original article atLive Science's Our Amazing Planet.
April Fools Day Recipe
Okay, there is always some April fooling going around on April 1st.
Start the day off with a wonderful breakfast of "ostrich eggs"! Some will refuseto eat them, but those who try it will realize ostrich eggs taste a lot like vanilla yogurt and peaches.
This is easy to do. Add vanilla yogurt to a bowl and then add half of a peach, round side up. It looks like an egg doesn't it?
Bench Tips by Brad Smith
April 2014THE HOUNDS TALE 1
April 2014THE HOUNDS TALE 1
POLISHING WHEELS
In the finishing sequence there's a step called pre-polishing, between sanding and buffing, and one of the most effective tools I've found to help here is the little silicone wheels used in a Foredom or Dremel. They come in several different abrasive levels and several different shapes. The wheels are color coded to denote their abrasive level. Different shapes (coin, knife, cylinder, point, etc) are available to match the geometry of the area being cleaned up.
For a starter, I'd suggest a medium, a fine and an extra fine wheel in both the coin shape and the knife-edge shape. The thicker coin shapes are particularly handy. Be sure to get a few extra mandrels so you'll have one of each wheel shape mounted and ready to go.
Cylinder shapes are nice for doing the inside of rings. Knife-edge shapes clean up the base of bezels quickly. Most jewelry catalogs carry these wheels, but often the color codes don't match between different manufacturers.
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RESHAPING SILICONE WHEELS
Silicone polishing wheels in the Dremel or Foredom are a great time saver, but after using them a bit they often need to be reshaped. This is particularly true with the knife-edge wheels.
The natural thought is to grab one of your files and hold it up against the rotating wheel to reshape it. But this gives you a problem. The grinding grit in the silicone wheel is much harder than steel, meaning that you end up grinding down the teeth of your file.
The best way to reshape your polishing wheels is to use a diamond file. If you don't have one and must use a steel file, I sacrifice the area of the file that is closest to the handle. That's an area which is not used in normal benchwork.
April 2014 Class Report, by Emie Stewart
Bezel-setting Fancy-cut Faceted Stones: Jurgen Maerz returns on April 26 and 27 to teach an advanced class in bezel-setting fancy-cut faceted stones such as marquis, pear, trillion, and emerald-cut. The class will cover the use of burs, creating a proper seat, removing excess materials, and the finer points of finishing. The class is full.
Precious Metal Clay: On April 2, John Crabb will teach a one-day class on using precious metal clay. Signups were at the March meeting, and the class is full.
Beginning Enameling: On Saturday, April 5, Barbara Maloney and Sue Poarch will teach a beginning enameling on copper class. Signups were at the March meeting.
Chainmaille: Helen Vaught’s monthly chain maille class will not meet in April because of the Easter holiday. Her class will resume on the 3rd Sunday of May, from 2 – 4 PM in the library. Students will need to bring two pair of smooth-jawed pliers. Helen will provide kits for purchase for each class. Signups will be at the monthly meeting.
Casting Lab: In May, Jack Spinks and Katiri Peters will be hosting the casting lab for those who have already had casting. Thursday, May 15, from 7 – 10 PM, is investing. Saturday, May 17, from 9 – noon, is the pour. Signups will be at the April meeting.
Big Saw Class: On the second Monday of every odd numbered month, Val Babineaux will be teaching how to use the big saws. The class will be from 6:00 – 9:00 p.m. The next class will be in May, with signups at the April meeting.
**Re Cabbing: The cabbing class is NOT a pre-requisite for other classes, including but not limited to, silversmithing. The cabbing class is a pre-requisite before members are allowed to use the lapidary equipment, which they may do only during open shop hours when a shop supervisor is present.
Arlie Bucks: If you are using Arlie Bucks for a class or lapidary shop, please make sure you sign them on the front so that we know they have actually been used rather than being misplaced.
Thank You: A HUGE thank you to the approximately 30 people who donated over 1500 hours of their time to teach classes and workshops at AGMC during January – October, 2013. While other clubs are dying on the vine, AGMC continues to experience robust growth, due primarily to active members just like you. If you are interested in teaching a class or workshop, please contact Emie Stewart at . Our instructors and supervisors are volunteers and do not get paid for their time. Thank you for the generous gift of your time and talent.
AGMC Facebook Page: The club’s Facebook page has over 300 fans! Visit the page regularly to see what’s new, and “Like” it and “Share” it with your Facebook friends. This is free advertising for the club and its annual show.
Class Postings: Please be considerate of your fellow club members during class signup times. A line usually forms just before 7:00 PM when the signup sheets for classes and workshops are posted. These sheets are posted at 7:00 PM on the hallway bulletin board at the clubhouse on the 1st Tuesday night of each month. They are usually posted a month before the class is scheduled to begin. Only current members in good standing, who have paid their membership fee, may sign up. Whenever possible, advance notice of upcoming signups is given in The Class Report and on the club’s Facebook page. The class schedule is emailed to club members approximately mid-month, and published in the club’s newsletter, available via email. When you sign up, please include your phone number and email in case the instructor needs to contact you. Also, please note the club’s no show policy, set forth below and on each signup sheet.
No Shows: If you sign up for a class and are unable to attend, you must let the instructor know before the class date so that they can offer your slot to someone on the waiting list. Failure to do so may cause you to be listed as a “no show.” Club policy is that no-shows will be wait-listed for future classes at the instructor’s discretion.
General Class Information: Class fees are $3/hr to cover building usage, plus any applicable supply fee as noted on the signup sheet. Students are expected to provide their own tools and materials except as noted on the signup sheet. The vast majority of instructors are volunteers who are not paid for their time but are willing to share their knowledge. Students are expected to follow instructor directions, cooperate in a classroom setting, and to observe all safety requirements. Failure to do so may be grounds for immediate removal from the class at the instructor’s discretion. Occasionally, outside professionals may be brought in to teach a class. These instructors are paid by the students, and the class fees are due at signup and are nonrefundable unless the Class Supervisor can fill the student’s seat before the class begins.
April 2014THE HOUNDS TALE 1
AGMC April 2014 Class Schedule
SPECIAL WORKSHOPS:
Precious Metal Clay
Wednesday, April 2, 7 – 10 PMInstructor: John Crabb
Beginning Enameling
Saturday, April 5, 1 – 4 PMInstructors: Barbara Maloney and Sue Poarch
Bezel Fabrication and Setting Fancy-cut Faceted Stones
April 26 – 27, all dayInstructor: Jurgen Maerz
ONGOING CLASSES:
Cab Class
1st Saturday, 1 – 4 PM Instructor: Ray Wilkes
2nd Tuesday, 7 – 10 PMInstructor: Stephen Bennett
4th Saturday, 1 – 4 PM Instructor: Barbara Maloney