Click here to view the "Meteorite Article Archive". Regmaglypts Part 1, Irons 2,7kg Henbury iron meteorite (Inventory # B-0099) from the Northern Territory in Australia with well preserved regmaglypts. The regmaglypts cover all surfaces indicating an individual flight history. Unlike most other specimens from the Henbury meteorite it is not a fragment or impact-shrapnel but an individual. Despite several thousand years of surface weathering the meteorite has lost only little material through corrosion. The stable patina visible on the specimen acted as an ideal protective layer against the forces of weathering. The curator is well advised to refrain from mechanical cleaning and to leave it in place. Heavily regmaglypted 4.971kg Sikhote Alin individual (inventory # B-0243). Most of the meteorite's surface has been smoothened by thermal ablation during the atmospheric passage. On several spots the melting progressed only partially and traces of the shear processes that occured during fragmentation can still be observed. This feature goes together with the fragmentation model as suggested by Krinow after which the Sikhote meteorite started to break up at a relatively low altitude. Thus the ablation process could not continue long enough to alter the complete surface of most fragments. Detail of the 4.9kg Sikhote Alin meteorite. Regmaglypts are basically exxagerated surface features of the body's original topography after fragmentation. Although it is true that protruding features like ridges and sharp angles are abraded in the plasma stream, the ablation process does not lead to even surfaces. This is due to micro turbulences caused by irregularities in the texture of the original surface. The plasma jet stream gets literally trapped within cavities and gourges of the surface and exxagerates these. The same effect can be observed on certain rocks from river beds. On meteorites this process is often illustrated by radial or spiral flow lines escaping from the center of a regmaglypt towards its rim. Slight orientation on a 5.9kg Sikhote Alin individual (# B-0151) in the shape of elongated regmaglypts radialling out from the center of the photo. The relation of length to width of regmaglpts as well as the orientation of the flow lines within elongated regmaglpyts provides good indicators for a stable flight phase of a given meteorite. The photo shows a 1.471kg Taza (NWA 859) iron meteorite (inventory B-0146). Mechanical and chemical weathering has already altered the regmaglypts of this meteorite. Prehistoric shafting and subsequent use as a club-head resulted in mushrooming of several edges. The chemical weathering has not progressed far but already the erasing effect of oxidation to the regmaglypts can be studied. In most hot desert environments regmaglypts tend to fray out and to expand while becoming less defined and more shallow, provided the meteorite is situated on top of the soil. In opposite to the ablation process in the plasma stream, chemical weathering in combination with mechanical weathering (e.g. sand blasting) levels the regmaglypts. However, if the meteorite is embedded in the ground other mechanisms come into play usually resulting in the exaggeration of regmaglypts. The above pictured specimen of the Gibeon meteorite was found by Manfred Gollub on his farm between Maltahöhe and Gibeon in 1985 and sent to Germany under the name of its find location. With dimensions of 42 x 36 x 6.6 cm the meteorite forms a flat oval shield narrowing towards frayed edges. Due to the thin profile of the shield shape the Maltahöhe mass weighs only 29.96 kg. One slightly concave surface is completely covered with small regmaglypts which show an average extension of 2 cm and an average depth of ~1.2 cm. The regmaglypts are distributed in a random pattern rather than in a radial orientation. Their depth increases towards the centre of the concavity, which is located ~ 8 cm off the geometrical centre and on the expanded end of the shield. Though no fusion crust is preserved the overall erosion on the Maltahöhe mass can be considered as very moderate. Regmaglypts are still clearly defined, extension cracks show only superficial caving or smoothing and the usual exaggeration of features common on Gibeon meteorites is absent. The image above shows a 9.1kg individual of the Campo del Cielo meteorite fall from the Chaco province in Argentinia (inventory # B-0242). Although the meteorite fell only ~4000 years ago, chemical weathering has proceeded further than in the case of the Taza meteorite which has a higher terrestrial age. The Campo del Cielo meteorite strewn field is located in a relatively humid environment and most specimens have been embedded in the sediments prior to their recovery. Salts contained in the soil added to the corrosion. Despite the agressive environment from time to time Campo meteorites show up that still display impressive regmaglyts. The image below shows the slightly concave rear surface of the above meteorite. Return to the "Meteorite Article Archive".   © 2001-2010 NigerMeteoriteRecon