Here is some fluorite (purple) and calcite (yellow) on sphalerite (silver). No further comments, I just thought this was pretty.
Stalactites and stalagmites form in caves when water that contains dissolved minerals (such as calcium carbonate) drips from the ceiling. Scientists can analyze the 18O/16O ratios (isotopes of oxygen) in the stalactites and see how the temperature changed as they were formed. A team led by Andy Baker, Gurinder Nagra, and Pauline C. Treble of the University of New South Wales, Australia discovered that Yonderup Cave had a lot more 18O than they expected. Since having more 18O is associated with higher temperatures at the time of formation, it could have been interpreded as one of the largest climate changes in the last 2 million years.
But, there was a wildfire in 2005 and a large tree died right on top of the cave. Baker’s team believes that this is what actually caused the increased 18O concentration. This is important for anybody else trying to use these oxygen isotopes to determine ancient temperatures, because if they get a very warm result it might have been caused by a forest fire instead.
It’s a little more complicated than that. Read the whole article here: http://cen.acs.org/articles/94/i30/Cave-dripwater-contain-fire-evidence.html and check Baker’s website for more interesting stuff about how he researches caves to learn about past climates.
At Mark Sherwood’s talk “Earth Science… Facts, Frauds and Scams” he mentioned carborundum (also spelled carborundrum). It is made of silicon carbide, but it is not a natural mineral that you can find in the ground. If you want to find some carborundum, look in a chimney. At an iron foundry, the carbon and silicon in the smoke rise and precipitate on the inside of the chimney. When the chimney is cleaned, they find these nice silicon carbide deposits. They are iridescent and pretty enough to buy, but don’t be fooled. Some sellers will say that carborundrum or moissanite and pretend like it is from some secret mine or even a meteorite, but it is really a man-made mineral.
Note: Moissanite is a naturally occurring silicon carbide, but it is very rare and it doesn’t look like the specimen pictured above. It actually looks like tiny green glass crystals. They are usually heat treated to increase clarity. If so, the seller needs to disclose that the specimen has been heated or they are being fraudulent. Buyer beware.
The Spring 2017 Gem and Mineral Show was very successful. The parking lot was filled to capacity and we made over $3000 for the scholarship fund. I think it helped that it was so cold on Saturday, because people wanted to do something indoors. Here are some of the highlights.
When you come to the show, don’t forget to enter the drawings for door prizes.
This hematite and magnetite specimen is from Patagonia, Argentina. Bruce got it at the Denver show and gave it to Sharon Penner. It’s about 4 inches long and pretty shiny.
In November 2016, we went to see Marv Dahmen’s collection of vintage Joplin/Tri-State mining equipment and minerals. He talked about it for 5 hours but there was never a dull moment. We managed to record some of it, although it was so long Stephanie and David ran out of space on their phones. Here are some photos.
Thank you Marv for inviting us on your property and into your home to see your amazing collection!
Rutile quartz is quartz that contains rutile inclusions. Rutile is made of titanium dioxide and usually forms long, thin needles. It is most commonly found in quartz, though it can also be found in sapphires. The inclusions are usually gold in color and can be seen in dense parallel fibers or as scattered needles. You can see both in this specimen.
This rutilated quartz sphere is smoky quartz with rutile inclusions from Minas Gerais, Brazil. It is on display at the Rice Museum in Hillsboro, Oregon near Portland, Oregon. If you are in the area, we highly recommend this museum.
Special guest article from Show-Me Rockhounds club members Dan and Connie Snow
Fairburn agates are a form of microcrystalline chalcedony, 100% silicon dioxide with a hardness of 6 ½ to 7 on the Mohs scale. They are also called fortification agates because of their banding. They were formed approximately 300 million years ago in an ancient limestone bed of an inland sea. To hunt Fairburn agates requires looking at every rock and turning many with a rock pick. It is strictly surface hunting no digging, mining, cracking or breaking rocks. The photos shown are exactly the way the agates were found, with no cutting, polishing or tumbling having been done.
Fairburn Agates found by Dan and Connie Snow. Collected from the Fairburn Agate beds of South Dakota and the Oglala National Grasslands in Nebraska.