Bitterroot Gem and Mineral Society
September 12, 2006
The Bitterroot Gem and Mineral Society began the meeting at seven thirty P.M., with the president, Don Contraman, leading the group with the pledge of allegiance to the American flag. There were 23 members present and 1 guest.
The program for the evening was presented by Nola Edgar, who brought many different specimens of fossils, rocks and minerals that came from Ohio. She explained the different strata that forms the different counties of that state, and showed us her finds from each area. She had a nice collection of trilobites, pronounced TRY-lo-bytes, that were ancient sea dwelling creatures that crawled or swam. They lived in the Paleozoic Era, between 570-260 million years ago. They were members of the phylum Arthropod, which includes, insects, spiders, crabs, shrimps, and centipedes. All of these animals have jointed legs segmented bodies and external hard skeletons called exoskeletons, which are molted as the animals grow. The last of the trilobites were seen in the Permian period of the Paleozoic Era. The presenter explained to us that trilobites are not often found whole. She joked that we would find lots of trilobits and trilobutts. Among her collection of trilobites, was the smallest specimen that this writer has ever seen! It was half the size of a small pea. Wayne Farley interjected that he recently read about a three foot long trilobite found in Canada, which holds the record. Mrs Edgar invited us to come and look at all the specimens she brought during the break. A warm hand of appreciation ended the presentation.
William Davis brought in a fine specimen fossil that he bought at the recent Gem and Mineral show in Missoula to share with the group. It was from the family Scapililda which is characterized by it’s unique J-shaped body chamber. Thank you William.
The program was followed by refreshments, provided by Jo Farley, Margaret Sharp, Chris Ponder, and Mildred Soll. Special thanks to Betty and Bill Hodge who brought apples from their trees to share with the group.
The business meeting began at 8:45 P.M.. Mildred Soll introduced Kathy Shell as our guest.
Old business. Regarding the Opal mine. Don Farley reports that Ralph Luther did all the work. He got the people, set up with the BLM and got all the permits, staked out where it was supposed to go, and hired the contractor to dig. When the machinery got up there, and commenced to dig, he hit too much basalt and couldn’t dig much. He dug in two areas, and we did find some blue, but it’s hard digging. Harvey Sharp brought in a specimen that he found to share with the group. Wayne Farley also brought in a piece that he found which had some fire in it, but failed to bring his microscope so we couldn’t see it. Wayne explained that there are two typical ways that opal can get fire in it. Typical opal, when looked at through an electron microscope is made up of little microspheres that refract the light into the various colors. You can also get a prism effect where the rock fractures into the prism and it will refract the light into the various colors. Jo Farley added that on Saturday there were nine members at the opal mine, and on Sunday, more came. By Monday, fifteen people were there. And she was very proud of our club for making such a big turnout. She’d like to thank everyone that came and she hopes that those who didn’t make it can come next time, because it was fun. Wayne Farley reports that he and his son stayed on top of the mountain while everyone else camped below on the river. When it became dark they took their black light to see if the opal in the new hole would fluoresce. But the only thing that would fluoresce was little seams of Chalcedony, which fluoresced bright green. Jo Farley reports that only four wheel drive high clearance vehicles should attempt the road to the opal mine. A little bit of work was done on the road, filled in a few holes, and the excavator had to do some work on a corner to get his rig through.
New business. Apple days. We are signed up for a booth, again, and will be looking for people to sign up for it. Apple days will be held on Saturday, October 7th, 9:00 AM to 4:00 P.M.. We will need a lot of help, as Jo Farley will have an out of town visitor that day and won’t be able to spend all day there. We also need contributions. Harvey Sharp has volunteered to do the garnet and sapphire table. We also need to get something going for the spinning wheel. Everybody check your calenders to see when you can work at the booth. We will have a sign up sheet for working at the booth and one for donating items for the booth.
Ellis Houseman reported on the Missoula show. There were about twenty cases upstairs. First place case was one all in black filled with sliced agates. Bob Riggs took first place on a belt buckle. Wayne Farley put in a couple of Tiffany style lamps, one had slabs of Mexican agates and the other had Montana agates. Ellis says all in all it was a very successful show, and when does the Hamilton club plan on a show?
Ellis Houseman wants everyone to think about getting a bus trip together to go to the Federation Show in Butte, next year. The show will be on the 3rd, 4th, and 5th of August, 2007.
Wayne Farley reports that he attended the Montana Council Meeting after the show. They are going to review the bylaws and present significant issues to their clubs to see if things need to be changed. Elections took place and officers were elected. Wayne is the president, again, and Ellis is treasurer, again. Ellis states that the next council meeting will be held in Bozeman, and he expects at least five members from this Hamilton club to attend.
Since no one volunteered to bring refreshments for the next meeting, those who attend will just have to do without, unless someone decides upon themselves to bring treats. Jo Farley said that no one knew she’d be back and everyone brought something to cover for her, just in case, and it worked out well. The president reports that it may be good or it may be slim.
The program for next week will be a lady from the Forest Service. She will present a program on the lay of the land up Lolo where we dig our smokey quartz crystals. It should be a very interesting program. Mildred Soll suggested that club members bring their crystals to share at the next program.
The club congratulates Ralph Luther for the very good job that he’s doing putting out the newsletter. Ralph states he just wants you all to read it! Kudos to Ralph!
The door prize was won by Sharlene Farley. She received a beautiful rock pendant given by Rose Houseman.
The 50/50 drawing totaled $19.00 and was won by our president, Don Contraman, who generously donated his half to the scholarship fund. Thank you Don.
Diane Ayers stood at the end of the meeting and thanked the club for the beautiful crystal trophy that her and the other original members received at the picnic. Don Contraman thanked her by saying that if it weren’t for her and the other members we wouldn’t be there that night.
The meeting was adjourned at 9:15 P.M.
Respectfully submitted by,
William Ponder
Bitterroot Gem and Mineral Society
September 26, 2006
The BGMS began the meeting at 7:30 P.M. with 30 members present and two guests. Don Contraman lead the group with the pledge to the American flag.
The program for the evening was presented by Wayne Farley. Wayne gave an interesting report on opals and the different kinds of opal he found at the opal mine. He explained how the colors come out in the opals and about the different kinds of opal. Opal is a noncrystalline form of quartz and has a hardness of 5-6. Silica freed into ground water from decomposing rocks may separate again at modest temperatures to form a sort of silica gel. Opal that forms as a low temperature deposit around geysers and hot springs is known as a geyserite. Opal that makes up the skeletons of the microscopic shells of diatoms and other organisms is called tripolite. Precious opal is essentially a clear material, characterized by a play of rainbow colors. Fire opal is a clear orange/red variety. Common opal has no particular value, is widespread, in volcanic rocks, and is often highly fluorescent (yellow/green). Clear colorless opal is known as hyalite. Opal and microcrystalline quartz can replace buried wood, making petrified wood. Wayne said that common opal makes up 99.99% of all opal. Wayne passed around many different specimens of opal including jelly opal, common opal, and fire opal. Wayne reports that the opal found at our claim is fragile and comes apart very easily. Wayne ended the presentation by showing us the beautiful fluorescence of the opal with his blacklight. Thank you, Wayne.
The refreshments for the evening were provided by Rose Houseman, Chris Ponder, Betty and Bill Hodge. Mildred Soll and Charles Taylor will bring the refreshments for the next meeting. A big thanks to Betty and Bill Hodge for sharing their wonderful home grown plums with the group.
Old business. The president wanted to know if anyone had been to the opal mine since the first weekend. Nobody went that we know of. Jo Farley reported that it was too wet.
New business. Apple Days. We still need people signing up to help at the booth. Jo Farley reports that we need as many tumbled rocks as we can get. If anyone is crafty, and can make little animals out of rocks, the kids will love these.
Harvey Sharp and Ellis Houseman want people to think about putting on a rock show for April. We’re thinking about having it at the seniors center in Hamilton. Jo Farley reminds us there must be a lot of electrical outlets to supply the vendors with. They need a lot of electricity to sell their wears. She also said that we need volunteers the day before to mark out the spaces for the vendors and help set up the tables. Harvey Sharp suggested that we also might have the kitchen involved for the rock show which would be a great asset. Suppose the Hellgate club would like to participate in this rock show? Margaret Sharp stated that it would take a lot of publicity for a good turnout. Also it would be important to have a lot of dealers there for a large display of different kinds of rocks. The president requests that Harvey Sharp get together a list of what kind of workers are needed and what is going to be involved in getting this show together. Security of the show was discussed. Joan Contraman suggested that if we could get vendors that have natural stone beads, we would attract a whole new group of people to the show. Don Contraman appointed Harvey Sharp as show chairman. Ellis stated that the show also needs a treasurer. Joan Contraman made a motion that Ellis and Harvey come up with a list of jobs that they should present at the next meeting, it was seconded and the motion was passed. Jo Farley ended the discussion by asking for a show of hands as to who was interested in helping with the show. It was a positive response.
Nomination Committee. Don Contraman states that we are rapidly approaching the end of the year and that new officers will be needed. Ralph Luther, Steve Vieth and Chris Ponder have agreed to make up the committee. Don’t be surprised if you get any phone calls because we are looking for officers for next year.
Jo Farley announced that if the weather permits there will be a field trip October 14th up Lolo to dig for smokey quartz.
The 50/50 drawing was won, once again, by our president, Don Contraman, who donated his half back to the club. The total was $21.00. Thank you Don.
The door prize was won by Rose Houseman, but since she won’t be here for the next meeting she graciously donated the prize to the next meetings winner.
The meeting was adjourned at 9:30 P.M.
Respectfully submitted by,
William Ponder
OPAL
Wayne Farley 09/26/06
Opal derives from the Latin opalus, meaning precious stone. Opal is an amorphous (i.e. noncrystalline), hydrated silicon dioxide (SiO2 * nH2O), that contains about 3-15% H2O by weight. The hardness of opal depends on its water content, and varies from 5.5-6.5, Water content can be quite variable, even within a single piece. The relatively high water content of most opal leaves it susceptible to damage by rapid or extreme changes in temperature. Opal mined from a damp or wet source, or that mined from volcanic host rock is more prone to dehydration than that mined from a dry source or from a sedimentary host rock. Dehydration may result in cracking (referred to crazing or checking) that greatly diminishes its value. The two major classes of opal are fire opal & common opal. A wide variety of names has been, and continues to be used, to describe various types of opal. Most have their basis in three important attributes; 1) body color; 2) transparency; 3) character of play-of-color and colors present. The following names are in common use:
- Black Opal- black, dark green, dark brown or other dark body color with vivid play-of-color. Often synonymous with " Australian Opal" or "Coal Black".
- Crystal Black Opal - Black opal that is transparent to translucent.
- Crystal Opal - transparent to translucent, having no body color but strong play of color.
- White Opal - translucent to opaque, with white body color and play-of-color. Once referred to as "Hungarian Opal".
- Boulder Opal - opal with play-of-color that is present in a matrix of dark brown or black sandstone (ironstone).
- Transparent or Semitransparent Opal - transparent opal with slight to no play-of-color with a body color that is yellow, orange, brown, red or colorless. Colorless called "Water Opal", "Jelly Opal", "Hyalite", "Contra-luz", "Hydrophane". Yellow, orange and red body color referred to sometimes as "Fire Opal" or "Cherry Opal". This material is commonly faceted rather than cabachoned.
- Common Opal ("Potch") - translucent to opaque, having nearly any body color, but no play-of-color. Known by a myriad of names; e.g. Matrix Opal, "Geyserite", "Wood Opal", etc.. "Common Opal" contrasts with "Precious Opal" in the categories above.
Fire Opal is unique among all gems because of its source of color (diffraction). The source of the play-of-color in fire opal is the semi periodic arrangement of the spheres of hydrated SiO2, whose centers are spaced at about the wavelength of visible light. These serve as a diffraction source for refracted and reflected light. Finer quality opal (that exhibiting great play-of-color) generally has more H2O than lesser quality material. Commercial deposits of Fire Opal have been found in Arizona, at the Spencer Mine in Idaho, Louisiana, the Virgin Valley in Nevada, and at Opal Butte in Oregon.
Common Opal, which has a random arrangement of SiO2 spheres, has no diffraction play of colors. However, common opal can be attractively colored yellow, brown, green, blue or pink by other trace elements or minerals. Common opal often forms petrified wood and is found in all of the western states.
Formation of Opal: Opal is formed at low temperatures (<200oC) by the precipitation of colloidal silica from groundwater moving through siliceous rocks in arid regions. Colloidal silica can derive from the following:
- Alteration of siliceous sedimentary rock (quartz sandstones) along cracks and cavities to deposit opal crusts or nodules - Australia
- Alteration of siliceous rhyolite volcanic rocks – Brazil, Mexico, Idaho
- Concentration of silica gel derived from marine organism in evaporating sea water; replacement of skeletal remains and shells by opal - Australia
Blue Grouse Opal Site
The Blue Grouse Opal Site, claimed by BGMS, is 99.99999% common blue or white opal occurring in fractures in porphyritic rhyolite flows. The visual phenocryst crystals in the rock are biotite. Occasionally, specimens have been found with pin point size flashes of fire opal. Rumor states that many years ago, the original claim holder found a fist size specimen full of fire. However, no one in our club has ever seen it. Jo Farley says that she has seen a couple of marble size specimens of fire opal that the Kaisers from Salmon, Idaho have found on the Blue Grouse Claim.
On Sept. 8, 2006, the BGMS hired an excavator and operator to dig on two areas of the Blue Grouse Claim. Ralph Luther spent the day at the Claim working with the excavator operator. Several people from the BGMS club searched the diggings for fire opal on Sept. 9th, 10th, and 11th. Jo Farley has the list of participants. On the 9th, the diggers were Robie Flynn, Bonnie Klein, Gayla Kaiser, Wes Williams, Jerry & Janice Sommers, Jo & Don Farley, and Ralph Luther. On the 10th, the diggers were Janet & Tim Huntley, former members Jim & Karen Rayner, Jo & Don Farley, and Penny & Ralph Luther. On the 11th, the diggers were Larry Jones, Harvey Sharp, Anna & Marvin Horner from Salmon, Jerry & Janice Sommers, Joe & Gayla Kaiser, Don & Jo Farley, Ralph Luther, and Wayne & Dan Farley. I, Wayne Farley, and my son Daniel searched on Sept. 11; during daylight for fire opal, and later that night with a long wave ultraviolet light for fluorescent specimens. We knew that the blue opal was fluorescent from previous years of collecting. I found a couple of pea size specimens of blue opal during the day search that had pin point flashes of color by examining numerous specimens with a 10 power hand lens. I then later examined these specimens at home with my 10 to 100 power microscope. One blue opal specimen had true green diffraction fire. The other specimen had a rainbow of colors from a fracture prism of opal. Samples of fire opal and fluorescent opal from the Blue Grouse and other areas were shown at the Sept. 26 club program.
Idaho Opal:
In Idaho, opal is the second largest contributor to the total value of gem material produced. The varieties produced include precious (white and pink), yellow, blue, pink, and common. The Spencer opal mine, the largest privately owned gem stone producer in the State, is the major producer of opal. At Spencer the precious opal occurs as one or more thin layers within common opal partially filling gas cavities within a rhyolite-obsidian flow. About 10% of the material is thick enough to cut into solid gems; the remainder is fashioned into doublets and triplets. The Spencer Mine is the source of pink common opal and pink precious opal. High silica volcanic ash deposits that derived from acid rock magma are believed to have been the source of the silica in Idaho’s opal deposits.
Differentiating Volcanics:
Acid magma produces Granite if cooled slowly, Rhyolite if cooled rapidly in surface flows, and Obsidian if cooled very rapidly. Basic flow rocks produce basalt, and are the chemical equivalent of Gabbro. Basic rocks are relatively low in silica and are not good sources for colloidal silica for producing opal. Volcanic rocks can be differentiated by their chemistry and physical characteristic as shown below:
Illustration by J. Johnson, USGS |
Basalt is the aphanites mineralogical equivalent of the coarse grained basic rock Gabbro. It is composed primarily of calcium plagioclase feldspar, pyroxene, minor olivine, and does not contain quartz or other light-color minerals. The overall color is dark grey to greenish black. It commonly has numerous bb to pea sized gas bubbles, which may be open or filled with secondary minerals. Basalt is never a source rock for opal, but rarely may be a recipient. Good examples of Basalt are the Columbian River Basalts in eastern Washington and Oregon, or Craters of the Moon in southern Idaho.
Rhyolite is the aphanites mineralogical equivalent of the acid rock Granite; and at times is porphyritic, meaning that it has scattered visual phenocryst crystals of quartz, sanidine (a potassium feldspar), biotite, and amphibole. Rhyolite colors vary from gray to reddish. The reddish tones are due to potassium feldspar porphyritic crystals in the rock. Rhyolites are generally found as flows, sills, and dykes, and occasionally as plugs. They never form widespread deposits because the viscous lava can only flow for short distances. Owing to their hardness and resistance to weathering, rhyolites often form jagged, angular, upstanding rock masses, and these features combined with their pale color make rhyolites relatively easy rocks to identify in the field. Acid volcanic rocks are more explosive than basic volcanic rocks, and rhyolite type rocks may also form as welded volcanic ash or welded volcanic breccia. These latter two are more susceptible to diagenesis of silicate minerals, and thus more favorable as a source for opal formation.
Fluorescent Opal:
Opal fluoresces in a variety of colors under ultra violet lights. Amongst the brightest is the clear botryoidal masses of Hyalite Opal from Spruce Pine, N. C. that fluoresce a bright green.
In Montana, about 25 miles south of Bozeman, fine Hyalite Opal and beautiful reddish-yellow translucent common opal occurs near the summit of Mount Blackmore, Gallatin County. This opal was discovered by geologist Albert Peale in 1872. One of the nearby peaks, Hyalite Peak (10,110 feet) has been named after the occurrence. The opal from this locality was once seriously considered for gem purposes and the name blackmorite proposed for it. A couple of pieces were for sale at one of the gem & mineral shows this summer.
I, Wayne Farley, also discovered this summer that common opal seams in the Crystal Park matrix fluoresces a bright green. I intend to follow this up next summer for good specimens. The fluorescent green in opal under the ultra violet light is due to a few PPM of uranium.
Editors Notes
I’m sorry that I had to squeeze this newsletter up a bit to get it on our maximum of 8 pages. I tried to get this out yesterday so it would remind you all of our Apple Day booth but was unable to do so. Also, I have not had time to proof read this newsletter so hope I didn’t make too many mistakes.
We are still hoping to have an outing on the 14th is the weather will cooperate. This outing is being guided by Bonnie Klein and coordinated by Jo Farley.
