nljan2009
The Cochise County Rock
Monthly Newsletter of the Sunsites Gem & Mineral Club
www.cochisecountyrock.org
“Finding and Grinding Rocks in Cochise County, Arizona since 1967”
January 2009
This issue edited by Don Hammer
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Sunsites Gem and Mineral Club General Meeting January 12, 2009
Our meeting begins at 7 as usual. Dr. John Ware will present “An Overview of Apachean Culture and Lifeways” at 8:00 pm at the Sunsites Gem & Mineral Club meeting on Monday evening January 12, 2009 in the Community Center. The public is invited to attend. Public presentations on Apache Indians nearly always deal with Apache history and most of these focus on a very thin 30 year slice of time at the end of the nineteenth century when various Apachean groups were engaged in intermittent warfare with US military troops and settlers. This talk is not about Geronimo, Cochise, or Apache raids and skirmishes with the cavalry. Instead, we’ll examine Apache families, communities, social and political organization, economy, and ritual life. What was it like growing up Apache? How were communities formed and organized? How did community life and economic pursuits change through the seasons? How were traditional Apache families constituted and kinship ties reckoned? Why are the Navajos so different from other Apachean tribes? The goal of the talk will be to present a more balanced portrayal of Apachean people, their history, and their fascinating culture.
Dr.Ware became executive director of the Amerind Foundation near Dragoon in 2001. He is a fourth generation Arizonan and has worked as an anthropologist in the Southwest for 40 years. His research and publications deal mostly with the peoples and cultures of the Colorado Plateau and he is currently completing a book on the social-political history of the Pueblo Indians of the Southwest. In addition to his research and writing, Ware has taught anthropology and archaeology at the college level for 25 years and is a former director of the Laboratory of Anthropology in Santa Fe. Ware graduated from Prescott College in 1973 and received his Ph.D. in anthropology from the University of Colorado in 1983.
Don, wanted to let you know that Dr. Scott Baldridge (a geologist from Los Alamos lab) will be at the Amerind on Monday, January 12th (the same day John Ware will be speaking at the Gem & Mineral Club). Scott will do a brownbag lunch in the Amerind library at 12:00 Noon followed by a brief hike around the property to look at the rocks. Thought the G&M Club members might be interested, and if they have any interesting rocks they would like to have identified, they could bring them along. Could you let the membership know? Thanks much, and any questions, just give me a call.
Jill Williams, Marketing/Membership
The Amerind Foundation, 520-586-3666
January Field Trip
We will go to the Round Mountain Fire Agate area NW of Lordsburg, NM. Plan to meet at the rest area at exit 20A in Lordsburg at 9:15 on Saturday January 24 to leave at 9:30 which will put us on site about 10:30. Lordsburg exit 20 A is 70 miles from Willcox exit 340 so plan accordingly. There is a Chevron Quick Stop at that exit for coffee. The collecting area is huge – over a square mile so plan on spending the day. Actually there are two sites the better of which requires high clearance but if you don’t have high clearance there is plenty of chalcedony at the first site. The better site has areas where chalcedony covers over half of the surface including roses and nodules and some of the chalcedony has actual fire agate. Bring light digging tools, buckets or bags, drinking and rock washing water, lawn chairs, lunch and sun protection. If we have rain the trip will be postponed so check the Web site and/or call Paul or Henri.
Lapidary and Silversmith Classes
Lapidary classes are in session on Thursday from 6:30 to 9:30 PM at the Lapidary Room behind the Fire Station. Show up or call Larry Strout at 826-3991. Larry is also available to teach silver soldering, a prerequisite to silver smithing. Keith McRobert will resume teaching silver smithing in early January. Call Don Hammer at 384-3105. Come and join the fun of lapidary, silversmith, and wire wrap lessons. Interested, any questions? Wire Wrap - call Larry Strout 826-3991.
Club Calendar:
January
12 General Meeting
24 Field Trip
29 Board Meeting
February
9 General Meeting
21 Field Trip
26 Board Meeting
March
9 General Meeting
21 Field Trip
April
2 Board Meeting
13 General Meeting
18 Field Trip
30 Board Meeting
May
11 General Meeting
16 Field Trip
28 Board Meeting
June
6 Club Picnic
Upcoming Regional Events
January
21-25 Quartzite Gem and Mineral Show. Gems, Minerals, Fossils and related hobbies. Daily field trips. For information powwow@qlaaz.org or www.qlaaz.org
30 – Feb 15 The Tucson show http://www.tucsongemshowguide.com/
February
27 – March 1 Denver Gem and Mineral Guild 2009 Show. Jefferson County Fairgrounds, Golden, CO. For information janiemube@comcast.net
March
12-15 The Deming Show. Jerry Abbey 575.546.4338
20-22 Albuquerque 40th Annual Gem & Mineral Show. Minerals, fossils, jewelry, beads. Hours 10 am to 6 pm. For information call Paul Hlava 505-255-5478.
Fire Agate is a layered stone. The layers are small enough that light entering them forms interference colors known as "fire". The gem is thought to be formed when hot water saturated with colloidal silica and iron oxide invades cavities in country rock and begin to cool. Chalcedony with iron oxide begins to grow on any available surface (the iron oxide gives the basic brown color to the gem). As the solutions began to precipitate and grow layers of silica and iron oxide would be deposited depending on the relative level of those elements in solution and underlying conditions. These alternating silica and iron oxide layers (Schiller layers) cause the brilliant fire in the gem. As iron oxide ran out in the solution colorless chalcedony continued to grow.
Many of these gems are found in the land between Kingman, Arizona and Needles, California, and around the Colorado River. Fire Agate has also been found in quantity in some areas of Mexico.
Cutting Fire Agate essentially reverses nature's process by grinding and polishing away layers, following natural contours, until only the fire is visible. The most common colors are reds, greens and oranges. Deep purples and blues are rare and generally demand higher prices.
Fire agate is a brown, microcrystalline quartz (chalcedony) which has a botryoidal (grape-like) growth form, and which contains layers of plate-like crystals of iron oxide (limonite) in various planes within it. The iridescent colors of red, gold, green and rarely, blue-violet, result from interference between diffracted light rays traveling through and reflecting off of these thin layers. (We see the same effect when looking at the rainbow colors at the surface of an oily puddle of water; or in the "orient" created by the layers of nacre on the surface of pearl.) Usually, fire agate pockets occur within specimens of colorless, white or light grey chalcedony.
Fire agate is found only in the US Southwest and Mexico and wasn't brought into commerce until after World War II. This, combined with the fact that it's one of the most difficult opaque materials to cut properly, keeps it scarce and mostly unknown to the general public.
In order to best reveal the colors, the overlying layers of chalcedony must be very carefully removed from the botryoidal surface creating a freeform shape with a carved upper surface. Just a tiny bit too much material removed kills the iridescence and too much left on dulls it. Such painstaking treatment requires substantially more time per piece by the lapidary, and tends to elevate cost. This type of fashioning also leads to a lack of calibrated pieces and has prevented the use of this gem in mass produced jewelry items.
Good fire agates are as impressive in their color display as fine black opal, but far less expensive. Additionally, fire agate is as hard and durable as any aggregate quartz making it wonderful for jewelry uses, including rings. The colors and form are rich and dramatic and generally appeal strongly to men (although I can personally attest to its appeal to women!)
The most desirable pieces show color over the entire surface with no "dead" spots. Red color is generally the most highly valued, but the few pieces with some lavender-blue are also highly sought after. The pattern of colors can be a value factor too. Similar to what is seen in opal, the colors can be tiny dots "pin fire", large blotches "harlequin" or, rarely, have a distinctive pattern such as circles or stripes. Well cut, carved and polished pieces with an attractive freeform outline are more valuable than those produced with a smooth crown and a standard cabochon shape.
Gemological Data
Makeup: silicon dioxide; Luster: vitreous
Hardness: 7; Crystal structure: trigonal
Fracture: conchoidal to granular
Cleavage: none; Density: 2.61
RI: 1.53-54; Birefringence: 0.004
Directions for Cutting Fire Agate
(Notes my father left)
Inspect the rough stone by wetting with water under a bright light. Direct light is ideal. (The stone is fragile so hold it over a padded surface.)
Observe the depth and location of color layers. The gem material (fire layers) are usually covered by chalcedony. Trim away excess chalcedony by sawing, grinding, or sanding.
Sawing should be used only for the top portion of chalcedony which has no color. Leave 1/8th inch for grinding.
For grinding, use a 100 grit wheel. Grind for not more than four of five seconds. Stop and examine for signs of fire under bright light. Shape the stone in any direction the fire indicates. Do not overheat the stone.
Remember -- Grind slowly and inspect often!
When you are satisfied that you have exposed all the fire, grind on a 600 grit wheel to eliminate scratches. Then start with 325 diamond paste, moving to 600, then 1200, 3000, and finally 50,000.
Reminder: In all of the above steps of grinding use plenty of water. Do not overheat.
Club Officers for 2009
President: Paul McKnight 520-824-4054
V.President:Henri Van den Bos 520 384-0288
Secretary: Jim Brower 520 826-4672
Treasurer: Walter Sigel 520-826-1009
Delegate at Large: Larry Strout520-826-3991
Hospitality Coord: Zoe Schnabel 520-826-0100
Past President: Don Hammer 520 384-3105