Shown above left are some very affordable specimens of Nantan which were offered for $10 each. Nantan was an observed fall during May of 1516 in Nantan, China. It is a nickel-iron meteorite which is structurally classified as a coarse octahedrite and chemically classified as type IIICD. The total weight of the Nantan fall is estimated to be approximately 9,500 kilograms. The strewn field is an 8 kilometer wide path, trending northwesterly over a length of 27 to 28 kilometers between the towns of Lihu and Yaozhai.
More than ten minerals have been found in the Nantan meteorites with kamacite and taenite dominant. Secondary minerals occurring in Nantan include plessite, scheribersite, triolite, graphite, spherlite, sideroferrite, dyslytite, cliftonite, and lawrencite. Widmanstatten figures are apparent in polished and etched slices of Nantan. Due to the strong weathering in a humid climate most smaller pieces of the Nantan meteorites turn brown and lose their melted surface. Smaller pieces buried in soils of lower valleys have been extensively weathered and oxidized into limonite.
Nantan meteorites represent one of the rare witnessed iron meteorite falls in the world. The Nantan fall was vividly recorded: "During summertime in May of Jiajing 11th year, stars fell from the northwest direction, five to six fold long, waving like snakes and dragons. They were as bright as lightning and disappeared in seconds". During China's "Great Leap Forward" during the late 1950s there was an effort to boost steel production with neighborhood blast furnaces. There was a shortage of available iron and so iron bearing rocks were searched for and dug up. Fortunately for meteorite collectors the melting point of the Nantan meteorites was too high and they were spared.
Needless to say, $10 space rocks have a lot of appeal to me. If I did not still have a handful of Nantan purchased from Kasper during a previous Show I would have snagged some of these without hesitation.
Shown above right is a handful of NWA 869 specimens, another very affordable meteorite. Kasper was offering these specimens from $3 to $28 each depending on their size. NWA 869 is a stony meteorite which was discovered in 1999 near Tindouf in Algeria. The total weight this fall has been estimated by various sources to be between 1200 and 3000 kilograms, making it one of the largest total known weight stony meteorites found to date in Northwest Africa.
Specimens of this meteorite vary rather widely which has complicated its classification. UCLA originally classified NWA 869 as an L4 chondrite, but later reclassified it to L5, which stands as it's current official classification. It has also been classified from L3.9 to L6 by a number of institutions around the world. Several of these classifications have also characterized NWA 869 as brecciated.
A common misconception on the part of the general public is that most meteorites are of the nickel-iron variety as opposed to the stony variety. This may be due to nickel-iron meteorites being more readily identified by lay persons as meteorites than stony types. However, approximately 80 percent of meteorite falls are chondrites. Chondrites are characterized by the presence of chondrules, which are small spheres of previously melted minerals that have come together with other mineral matter to form as solid rock. Chondrites are regarded to be among the oldest rocks in the solar system.
When cut and polished, NWA 869 matrix is full of color and chondrules. Some specimens of NWA 869 also display what appear to be carbonaceous inclusions and some also show clear brecciation, while others do not.
If I did not still have a handful of NWA 869 purchased from Kasper during a previous Show I would also have snagged some of these without hesitation.
Shown above left is a group of specimens of yet another nickel-iron meteorite which can be silverpicked with relatively modest damage to the billfold. These are specimens of Sikhote-Alin. Sikhote-Alin is one of the most spectacular falls of recorded history and one of a very small number of recent iron meteorite falls. Sikhote-Alin fell during morning daylight on February 12, 1947 in dense forest in the Sikhote-Alin Mountains, 25 miles from Novopoltavka, Maritime Province, USSR. Witnesses reported a shower of fireballs brighter than the sun which left a trail of smoke and dust 20 miles long that lingered for the remainder of the day. As Sikhote-Alin entered the Earth's atmosphere some of it began to break apart and this group of fragments fell together. When the descending group of meteorites reached an altitude of approximately 20,000 feet, the largest mass appears to have exploded into numerous fragments.
Light and sound from Sikhote-Alin were observed for two hundred miles around the impact, which produced 106 impact holes over an area covering about half a square mile, the largest being 85 feet across and 20 feet deep. Many fragments up to 300 kg in weight and totaling over 23000 kilograms were found scattered inside and outside the holes.
Specimens from this fall are of two general types. Some Sikhote-Alin specimens known as "complete individuals" exhibit ablation and fusion crust. These are probably pieces that broke off of the main mass at high altitude early in the decent. Their surface is vaporized and eroded by atmospheric heating. These specimens are characterized by regmaglypts, also known as "thumb prints", which are ablation cavities in the surface of the specimen.
The other type of Sikhote-Alin specimens are the "cold worked" fragments. Fragments exhibit the violent effects of being being blasted apart. These were probably produced by the low altitude explosion or upon impact with the ground. Many fragments resemble shrapnel.
Structurally Sikhote-Alin is classified as a coarsest octahedrite. The Widmanstatten figures are so large on Sikhote-Alin that no crystal structure may be apparent on small specimens when they are polished and etched. Chemically Sikhote-Alin is classified as type IIB. Minerals found in Sikhote-Alin include kamacite, taenite, plessite, schreibersite, rhabite, troilite and chromite.
Due to the large amount of Sikhote-Alin which fell and has made its way to market, it is one of the most affordable meteorites available to collectors. Kasper was offering Sikhote-Alin specimens from the group shown above left for $1.50 per gram. Some of these appeared to be oriented and exhibited flow lines. Note the flow lines on the specimen shown above right, with a penny providing scale. This piece of Sikhote-Alin weighed in at 79 grams and wanted $118.50 to go home.
Kasper also showed and offered micromount sized specimens of NWA 1068, which is a Martian meteorite discovered in the Moroccan Sahara during 2001 by a French team of collectors. They recovered 23 stones consisting of a larger single mass weighing 522 grams and 22 small fragments weighing less than 20 grams each. The total known weight of this fall is approximately 700 grams. Specimens of NWA 1068 are greenish-brown and partially coated by desert varnish. They do not exhibit fusion crust and cracks in them are filled with terrestrial calcium carbonate. Thin shock veins and small melt pockets are reported to be abundant in this meteorite.
NWA 1068 is classified as an SNC olivine-phyric shergottite. It has been published as the closest SNC to match the results of the Mars Pathfinder soil and rock analysis. Kasper showed 6 small specimens in magnifier type thumbnail boxes which wanted between $150 to $200 to take home your very own piece of Mars. When I inquired as to the weight of these NWA 1068 specimens, Kasper related he had not bothered to weigh them but he very roughly guesstimated the weight of each specimen to be in the neighborhood of 100 milligrams.
Shown in hand at left with a penny providing scale is a somewhat larger and more aesthetic specimen of NWA 1068 offered by Kasper which weighs in at 2.9 grams. This slice of Mars wanted $6000 to go home. While gold is dirt cheap by comparison, I note that 2.9 grams (14.5 carats) of ho-hum terrestrial diamond can easily set you back significantly more...
GeoFactum, Arizona Mineral and Fossil Show at the Vagabond Plaza Hotel (formerly the Ramada Inn) - WWW: www.geofactum.de Email: firstname.lastname@example.org Kasper von Wuthenau, Diplomgeologe, DorfstraBe 13, 19246 Techin / Germany - Fax: +4940432554061
While browsing at the Vagabond Plaza show I stopped by to check out Blaine Reed's of Blaine Reed Meteorites offerings in room 110. I was quickly drawn to the box of sliced and etched pieces of the Gibeon meteorite depicted above left. The total weight of the Gibeon fall is unknown, but enough of it has been found and collected to make Gibeon one of the more affordable meteorites available to collectors. These slices of Gibeon were offered by Blaine at $1.00 per gram. I couldn't resist one of the larger specimens weighing in at 31.2 grams which is shown in hand above right, and this extraterrestrial went home with me.
Gibeon was apparently a large nickel-iron meteorite that burst high in the atmosphere and fell in Great Namaqualand, Namibia, Africa during prehistoric time. Gibeon fragments are spread over a strewn field 70 miles wide by 230 miles long - one of the largest known strewn fields in the world. No Gibeon craters have yet been identified.
Some Gibeon specimens exhibit shrapnel-like features and "cold working" (bending and hammering-like deformations). Other Gibeon specimens exhibit regmaglypts, which are depressions resembling thumbprints that are produced on the surface of some meteorites during their atmospheric transit by material ablating off their surface.
Gibeon is structurally classified as a fine octahedrite and chemically classified as type IVA. The minerals kamacite and taenite are the principle constituents of this meteorite. Other minerals identified in Gibeon fragments include troilite, chromite, daubreelite, enstatite and tridymite. Radiometric dating indicates the crystallization of taenite and kamacite in the Gibeon meteorite took place more than 4 billion years ago.
Light kamacite bands bordered by darker taenite ribbons are characteristic of the Widmanstätten pattern displayed by polished and etched Gibeon. Because Widmanstätten figures are readily recognized and associated with meteorites by the public at large and because this slice is of an appropriate size and shape, I plan to incorporate my newest extraterrestrial in a future bola tie project.
Blaine Reed Meteorites, Arizona Mineral and Fossil Show at the Vagabond Plaza Hotel (formerly the Ramada Inn) Room 110 - PO Box 1141, Delta Colorado 81416 - Phone: 970.874.1487 Fax: 970.874.1487
While browsing at the Pueblo Inn show I happened across this box of black tektites from Maoming City, Guandong Province, China on a table outside Top Geo Ltd. Co.'s room 116.
Tektites are not well understood and their origins are still somewhat controversial. Tektites are sometimes irregularly and sometimes regularly shaped nodules of glass like substances. They are similar to obsidian in that they lack crystal structure but do not seem to be associated with volcanic processes. A popular theory regarding the origin of tektites involves meteorite impacts. They may be fused glass formed during impacts of meteorites with the Earth's surface. Different localities produce characteristically similar tektites which seem to be loosely associated with meteorite craters. The unique and diverse chemistry of various tektites could be the result of particular types of meteorites impacting particular rock types, with unique combinations producing a variety of effects.
At $5 each I figured I better snag one of these black tektites for potential use as accent material on a meteorite bola tie I have in mind, so the specimen shown in hand went home with me.
Need more input? For additional information on meteorites be sure and check out the books Rocks from Space and The Robert Haag Collection of Meteorites in the References for Rockhounds catalog at Bob's Rock Shop!