Snapshots from the Tucson 2006 Gem and Mineral Show
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by Bob's Rock Shop

Tuesday, Feb 1st, cloudy, breezy and a bit chilly in the morning, warm and sunny by early afternoon.

Ammonite sculpture, 32" overall, $1500 keystone

In October 2005 meteorite hunter Steve Arnold employed a sensitive metal detector to search the rural Kansas strewn field of the previously discovered Brenham pallasite. Brenham is the most plentiful pallasite known with over 3 tons of Brenham estimated by some sources to have been recovered and collected since the fall was first recognized as a meteorite by homesteader Mary Kimberly in the 1880s. A relatively small meteorite crater called Haviland that was serving as a buffalo wallow in the Brenham field was studied and excavated in 1929 using teams of horses and road scrapers by Dr. Harvey H. Nininger. Dr. Nininger's historic work on Arizona's Meteor Crater was instrumental in laying the foundation for the recognition of impact craters by the scientific community at large to be caused by impacts of extraterrestrial objects as opposed terrestrial geologic processes such as sinkholes, volcanic craters and steam blowouts. Material from Brenham has been found up to 1000 miles away, transported by Native Americans and buried in mounds over 1,500 years ago by the Hopewell people who were part of a huge trading network stretching across the central United States.

Steve's reworking of the Brenham strewn field proved fruitful, resulting in the find of a 1400 pound oriented specimen, which is the both the largest pallasite recovered in the United States, the largest known oriented pallasite in the world and now considered the main mass of the Brenham fall. This specimen, pictured above left and right, is on display during the 2006 Tucson Show on the courtyard side entrance to the lobby of the Inn Suites.

Meteorites are broadly classified as either irons, stones or stony-irons. Irons contain approximately 98 percent nickel-iron, stony irons approximately 50 percent, and stones up to approximately 20 percent. Irons constitute about 30 percent of all the meteorites which have been found and identified as such, but irons are actually rarer as a type than this statistic seems to indicate. This is due to the irons being much more recognizable as meteorites or simply unusual than the stones, which are more difficult to differentiate from terrestrial rocks. Of all the meteorites known from witnessed falls, more than 94 percent are stones.

Pallasites are a type of stony-iron meteorite, which is the rarest general type, The stony-irons are mixtures of nickel-iron and silicate minerals believed to originate within the mantle of a differentiated parent body. Stony-irons are classified as either pallasites, mesosiderites or lodranites. Pallasites are primarily composed of nickel-iron and olivine, mesosiderites of nickel-iron and eucrite/diogenite, and lodranites of nickel-iron, bronzite, feldspar, olivine and triolite.

Pallasites are the most common type of stony-irons but are rare meteorites, with probably less than one percent of all meteorites being pallasites. The lodranites are very rare with a small number of this type of stony-iron known.

Pallasites generally contain about equal volumes of nickel-iron and olivine, with the olivine enclosed in a continuous network of nickel-iron. The olivine to nickel-iron ratio can vary considerably from pallasite to pallasite and even within a particular specimen. A sliced example of Brenham is depicted at right. Brenham specimens vary from almost pure nickel-iron to a 2:1 ratio of olivine to nickel-iron. The nickel-iron has octahedrite structure and exhibits Widmanstatten figures when etched.

The record Brenham specimen found by Steve Arnold is further distinguished by way of being an oriented meteorite, which differ from most meteorites in maintaining a stable orientation rather than tumbling as they plunge through the Earth's atmosphere. Oriented meteorites become distinctively convex shaped as atmospheric friction heats and ablates the material from the extrados (leading) side, which is sometimes covered with flow lines or regmaglypts (thumbprints). Note the dome shaped extrados side of Steve's find, which is reminiscent of the heat shields on the Mercury, Gemini and Apollo space capsules. Oriented meteorites were studied by rocket scientists early in the U.S. space program to help determine the most effective shapes for re-entry heat shields on NASA spacecraft and ICBM delivered nuclear warheads.

Pictures from search and recovery operations and additional information regarding Steve Arnold's new find are presented at

Slice of Imilac pallasite, Atacama Desert, Chile, approximately 5" overall, 120.5 grams, $3000 Imilac, a gorgeous pallasite, found in Chile's Atacama. DATE OF FIND: 1822, T. K.W: 920 Kg (approx)

Slice of NWA 2995 newest Lunar meteorite, main mass 524 grams, approximately 4" overall, found in November 2005, and was just classified. Feldspathic breccia containing many highlands fine-grained lithologies and is further characterized by large amounts of breccia-within-breccia.

Slice of NWA 2200 Felspathic-breccia Lunar meteorite, approximately 2" overall, not for sale A completely crusted 552 g ellipsoidal stone found in the Atlas Mountains, Morocco purchased in 2004 August. Breccia consisting of coarse, greyish to whitish lithic and mineral clasts in a darker glassy to finely crystalline matrix. Lithic clasts are mainly very fine grained, quench-textured, feldspathic rocks that probably result from impact melting of anorthositic to gabboic anorthositic precursors. A small percentage of the clasts are ophitic-textured mare basalts.

Slice of NWA 482 Lunar impact-melt breccia, Algeria, 9.28 grams, approximately 2.5 inches overall, $18,000 exact location of find is unknown, but it is probably in Algeria. The stone is complete, oriented, and appears relatively unweathered. texture is typical of a crystalline impact melt breccia (polymict) with highland affinities; glassy and vesicular melt veins and melt pockets indicate shock subsequent to compaction by an impact event

NEA 001 Lunar breccia, 34.5 gram endcut, about 1.5" overall 262 g stone found by a prospector in northern Sudan in 2002 April. a clast-rich anorthositic regolith breccia containing numerous mineral fragments and lithic clasts embedded in a well-consolidated microcrystalline impact melt matrix. Lithic clasts (up to 1 cm in size) are mainly of anorthositic lithologies; impact-melt breccias of anorthositic composition are abundant and show commonly breccia-in-breccia textures. Fragments of primary igneous rocks of anorthositic to gabbroic composition are common,

Los Angeles 001 Martian achondrite, shurgottite, approximately 2" overall, complete slice, 9.85 grams, $19,700 Location: Los Angeles County, California initially found somewhere in the Mojave Desert in California Found: October 30, 1999 Type: Shergottite (SNC)

Slice of Zagami, Martian, approximately 5" overall, 74.7 grams $44,000 A single 40 pound stone was observed to fall near Zagami Rock, Katsina Province, Nigeria on October 3, 1962. A SNC meteorite, Zagami is believed to have originated on the planet Mars and to be a sample of the Martian crust that was in some way ejected from the surface through asteroid impact. Classified as a calcium-rich eucrite achondrite with a young crystallization age relative to other meteorites of 1.3 billion years, Zagami represents an extremely rare class of meteorite.

Smaller slices of Zagami, Martian, from 1.43 grams for $1200 to 10.12 grams for $7000. The 10.2 gram slice was approximately 2" across.

Allende carbonaceous chondrite $10 per gram JT Wasson numbers and ASU labels, approximately 2" piece of a number offered The Allende meteorite fell at 1:05 AM on February 8, 1969. It created a huge fireball, then shattered and rained fragments over the area of the strewn field. Allende is estimated to be several tons. Two tons were collcted after the meteorite fell, but specimens are still being found. It is possible that an accurate estimate may never be known. Chondrules (from which chondrites are formed) are thought to be among the oldest materials in our solar system. Scientists think that they were formed about 4,550 million years ago, when the first solid matter was forming. That makes the meteorite about 700 million years older than the oldest rocks on Earth! Clumps of white material--many with finger-like projections--are found throughout the meteorite. When analyzed these are mixtures of high temperature oxides and silicates of calcium, aluminum and titanium. They have been named calcium-aluminum inclusions, or CAIs for short. Scientists believe that these are among the first matter to have crystallized. They are older than the Earth itself. contains fine-grained, microscopic diamonds with strange isotopic signatures that point to an extrasolar origin; these interstellar grains are older than the Solar System and probably the product of a nearby supernova.

NWA 2140 Erfoud, Morocco 2003, CV3, largest piece in box above right approximately 2.5" overall, $5.00 per gram. The closer view of this material at left is the cut face of an approximately 3" overall end piece.

Slice of Muonionalusta fine (IVA) Octahedrite, found in 1906 near Kiruna, Sweden, approximately 12" overall, 2501 grams, $4000 Stishovite was reportedly found for the first time in Muonionalusta, suggesting shock metamorphic conditions in the parent asteroid during a cosmic impact event.

Iron meteorites are composed primarily of various alloys of iron and nickel derived from molten planetary cores broken apart billions of years ago. The metallic crystals responsible for Windmanstatten patterns only form in the vacuum of space where the molten pieces of planetary cores require millions of years of cooling to solidify.

Michael Farmer Meteorites, Arizona Mineral and Fossil Show at the InnSuites Room 184 (475 North Grananda) - WWW: Email: PO Box 86059, Tucson, AZ 85754 - Phone: (520) 743-3007

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