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”

December 2009

This issue edited by Don Hammer

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The next General Meeting of the Sunsites Gem & Mineral Club is on Monday December 14 at 6 pm at the Sunsites Community Center. Our program will be our Christmas party. We will postpone the best specimen contest to the January meeting.

November 9, 2009 General Meeting Minutes

Meeting called to order at 7:08.

Item 1: Minutes from previous meeting approved as published.

Item 2: Treasurer’s Report. Walter Sigel reported that the new account balance was $2,221.59. New funds came from membership dues, raffle tickets and the bake sale. The report was approved as given.

Item 3: Bake Sale. Diane Dunn reported that the bake sale though netting only $71 was worth the effort in terms of exposure for the Club as well as community involvement. She recommended that

next year the bake sale be held in the spring when more consumers frequent the market. Paul asked for an informal show of hands in favor of a spring bake sale and enough members showed interest

to go ahead with that plan.

Item 4: Lapidary room move. Paul explained that the possibility of a move was in flux at this time because of changes on the part of the Fire Dept. and that for the moment we would have to await further developments.

Item 5: Field trip report. Bob Fenner who will be leading the field trip began by strongly emphasizing the requirement to follow the safety

protocols as published in the last News Letter. These protocols will be enforced as a safety measure. Members will meet in the south parking lot at Gas City in Benson at 8:30 on Saturday. Departure at 8:45 sharp because of the long distance to the site. The field trip will

take place near Aravaca to search for geodes. Light digging and cold chiseling tools will be helpful. The last 20 miles before the site will

be on good dirt road with a 1/2 mile walk to the site. High clearance vehicles will be necessary and car pooling is recommended.

Item 6: Nominations committee report. Don Hammer reported that he and Diane Dunn were recommending Paul McKnight for president,

Jack Light for vice-president, Jim Brower for secretary, Walter Sigal for treasurer, and Glen Wirshing for member at large. Paul then called for nominations from the floor and as none were

forth coming the motion was made to close nominations. The motion was seconded and the recommended slate was approved unanimously by voice vote.

Item 7: Christmas Party on December 14 at 6:00. Information to help in preparations for the party will be published in the next News Letter.

Refreshments consisted of left over baked goods from the bake sale.

After the intermission, the contest was held for the best garnet finding from the October field trip at Three Sisters Mountain. The winner was Wallis Hozjan who received free raffle tickets.

Following the raffle, our guest speaker, Eric Easton from Vail, Arizona gave an interesting and informative talk on the subject of meteorites. His discourse covered needed equipment in searching for meteorites, the best places to find meteorites, how to recognize meteorites and methods of confirming a find as being a meteorite. As part of Eric’s presentation, he passed around a box with several meteorite-like stones and one meteorite, asking members to pick out the true meteorite. Only a few individuals picked out the real meteorite, demonstrating how difficult it is to identify these rocks from outer space.

Respectfully submitted,

Jim Brower, Secretary

November Field Trip

On Saturday November 14 16 members and two guests assembled at the Gas City parking lot in Benson and started off at 8:50 down I-10 to 83 and then Sahaurita Road to I-19 and Arivaca Road to Arivaca and SE into the forest for another 20 miles. We arrived at the parking spot at noon and decided to have lunch before going to the collecting site. After lunch we walked about ¼ mile down the wash encountering a large vein of rhyolite with thousands of small embedded geodes. We climbed up the east side following the same vein and found small geodes lying all over the ground. Those that did a little digging found some larger, nice specimens. Broken geodes with nice crystals littered the ground. After an hour or so most of our pails and bags were getting heavy and we headed back to the vehicles and drove back through Arivaca to I-19 enjoying the scenery along the way. That section of the forest is quite scenic. We thank Bob and Barbara Fenner for organizing a very productive trip into a beautiful area.

Christmas Party

The Club Christmas party will be held on our regular meeting date, the second Monday, December 14. But the meeting time is changed to 6 PM. The Club has two 20 lb turkeys which Diane Brower, Diane Dunn and Ann Wildauer will cook along with stuffing and gravy. Joan Hammer will make mashed potatoes. If your last name begins with A-H you are asked to bring a vegetable dish, I-P a salad or garnish, and Q-Z a dessert. Also, if you would like to participate in the gift exchange, please bring a preferably rock or club related gender-neutral gift - under $10 and gift-wrapped. If you plan to attend, please call Zoe Schnabel at 826-0100 before December 9. Do it now before you forget and leave a message if she’s not home. Let’s all come out and kick off the holiday season in style.

Lapidary and Silversmith Classes

We are ready to resume our various classes. Call Larry Strout at 826-3991 if you would like to attend lapidary or wire wrapping. Larry is also teaching silver soldering, a prerequisite to silver smithing. Keith McRobert will resume teaching silver smithing. Call Don Hammer at 384-3105. Join the fun of lapidary, silversmith, and wire wrapping.

Dues

Dues are due. The Board proposed and the members approved an increase to $15 for individuals and $25 for a family. Bring your dues to the next meeting or mail your check to Sunsites Gem & Mineral Club, PO Box 87, Pearce, Arizona 85625.

Club Calendar:

December

14 Christmas Party

23 Board Meeting

January 2010

11 General Meeting

23 Field Trip

28 Board Meeting

February

8 General Meeting

13 Field Trip

25 Board Meeting

March

8 General Meeting

13 Field Trip

April

1 Board Meeting

12 General Meeting

17 Field Trip

29 Board Meeting

May

10 General Meeting

15 Field Trip

27 Board Meeting

June

5 Club Picnic

Upcoming Regional Events

January

8-10

Phoenix - 38^th Flagg Gem and Mineral Show. Jewelry, gems, beads, fossils, minerals and lapidary supplies. 9 am to 5 pm. Mesa Community College, west parking lot. www.flaggshow.info.

Geodes (Greek γεώδης - geōdēs, "earthlike") are geological rock formations which occur in sedimentary and certain volcanic rocks. Geodes are essentially rock cavities or vugs with internal crystal formations or concentric banding. The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and/or chalcedony deposits. Other geodes are completely filled with crystal, being solid all the way through. These types of geodes are called nodules.

Formation

Geodes can form in any cavity, but the term is usually reserved for more or less rounded formations in igneous and sedimentary rocks, while the more general term "vug" is applied to cavities in fissures and veins. They can form in gas bubbles in igneous rocks, such as vesicles in basaltic lavas, or as in the American Midwest, rounded cavities in sedimentary formations. After rock surrounding the cavity hardens, dissolved silicates and/or carbonates are deposited on the inside surface. Over time, this slow feed of mineral constituents from groundwater or hydrothermal solutions allows crystals to form inside the hollow chamber. Bedrock containing geodes eventually weathers and decomposes, leaving them present at the surface if they are composed of resistant material such as quartz.

Coloration

Most geodes contain clear quartz crystals, while others have purple amethyst crystals. Still others can have agate, chalcedony, or jasper banding or crystals such as calcite, dolomite, celestite, etc. There is no easy way of telling what the inside of a geode holds until it is cut open or broken apart. However, geodes from any one locality usually have a more restricted variety of interior mineralization.

Geodes and geode slices are sometimes dyed with artificial colors. Samples of geodes with unusual colors or highly unlikely formations have usually been synthetically altered.

Prevalence

Geodes are common in some formations in the United States (mainly in Indiana, Iowa, Missouri, Kentucky, and Utah). They also are common in Brazil, Namibia, and Mexico. A large geode was discovered in Put-in-Bay, Ohio in the early 20th century. It is known as Crystal Cave, and tours are possible during the summer. In 1967, Iowa designated the geode as the official state rock, and it has a Geode State Park.

Keokuk, Iowa is known as "the geode capital of the world" for very good reason. A virtually countless number of geodes has been collected from the Keokuk area over especially the last 150 years. There are no less than 300 outcrops of the Lower Warsaw Formation that the geodes are found in within a 100 mile radius of the city. The main exposures are found in streambeds that are tributaries of the Mississippi River. (Sinotte, 1969; Hess et al. 1998). The two predominant types of rock in the Lower Warsaw Formation are argillaceous dolomite and dolomitic mudstone. The geodes found loose in creek beds originated in the Lower Warsaw Formation, but over time weathered out of the rock and fell into the creek, with many being transported downstream away from their source. In some locations where the Lower Warsaw Formation is right along the creek bank or even in the creek itself, it is advantageous to collect geodes right after a heavy rain that may cause a rise in both the creek level and the water current as fresh geodes may be loosened or dislodged from their host rock due to the faster-moving water (for your safety, wait until the water goes back down, however!).

Minerals in Keokuk Geodes (Primarily from the Warsaw Formation)

The following minerals have been positively identified as being in Keokuk geodes, as well as those previously published to exist or are currently under study.

Quartz- Lines almost all geodes. Clear, smoky, sea-green, iron-stained (orange), and pink or cherry tinted geodes are found. Clear and iron-stained geodes are the most commonly seen type of quartz geode. To date, research findings have not confirmed the presence of "citrine" geodes in the Keokuk, Iowa area. All such samples have been identified as iron-stained geodes. Citrine is considered by many geologists and gemologists to be rather uncommon or infrequent anywhere on Earth, and is considered by many in the gemological sector to be more uncommon than amethyst.

Club Officers for 2010

President: Paul McKnight 520-824-4054

V.President: Jack Light 520 824-4774

Secretary: Jim Brower 520 826-4672

Treasurer: Walter Sigel 520-826-1009

Delegate at Large: Glen Wirshing 520-826-0167

Hospitality Coord: Zoe Schnabel 520-826-0100

Field Trip Coord: Henri VandenBos 520 384-0288

Past President: Don Hammer 520 384-3105