Shipping & handling
fees free for all items on this site!
Frais
de port offerts pour toute commande passée sur
ce site !
Oum
Dreyga
Gour
Lafkah, Western Sahara
Fell 2003 16 October, 02:00 UT
Ordinary chondrite (H3-5)
Latitude: 24°18'N
Longitude: 13°6' W
On
16 October 2003, Moroccan soldiers stationed in Western
Sahara saw a meteorite falling on Gour Lafkah Mountains,
south of Zbayra, about 21 km from Oum Dreyga. The meteorite
fell near a 670 km long wall built in 1985, protected
by antipersonnel mines, and guarded by soldiers. About
17 kg were recovered. Stones from this fall were later
brought to Moroccan dealers. Most of them have been
collected after a rainfall and are thus slightly oxidized.
However, some fragments have been picked up soon after
the fall; these are very fresh. Fragments have been
sold under the names Amgala and Gor Lefcah. Classification
and mineralogy (M. Bourot-Denise, MNHNP): very fresh,
with a black fusion crust; H3-5 breccia (Fa16.7± 6.0;
19.5 ± 0.8; Fs14.4 ± 4.4; 17.4 ± 1.3),
S4, W0. Specimens: type specimen 20 g and two polished
mounts, MNHNP; one 1 kg complete stone and 30 fragments
totalling 862 g with Philippe Thomas.
Info: classified M. Bourot-Denise, MNHNP; main mass, Thomas.
" An ordinary chondrite from
the H group that is a breccia of
components ranging from petrologic type
3 to type 5."
The highlighted words are defined as follows:
Ordinary chondrite: A major
class of chondrites, distinguished by sub-solar Mg/Si and refractory/Si
ratios, oxygen isotope compositions that plot above the terrestrial fractionation
line, and a large volume percentage of chondrules, with only 10-15 vol%
fine-grained matrix.
H group: The high-iron
(H) chemical group of ordinary chondrites, distinguished by their high
siderophile element content, relatively small chondrules (~0.3 mm), and
oxygen isotope compositions that are closer to the terrestrial fractionation
line than those of other ordinary chondrites.
Type 3:
Designates chondrites that are characterized
by abundant chondrules, low degrees of aqueous
alteration, and unequilibrated mineral assemblages.
Many of the low-Ca pyroxene grains are monoclinic
and exhibit polysynthetic twinning. The type
3 chondrites may be divided into subtypes ranging
from 3.00 (least metamorphosed) to 3.9 (nearly
metamorphosed to type 4 levels). If primary igneous
glass occurs in the chondrules, it belongs to
type 3.
Type 5:
Designates chondrites that have been metamorphosed
under conditions sufficient to homogenize olivine
and pyroxene, convert all low-Ca pyroxene to
orthopyroxene, cause the growth of various secondary
minerals, and blur chondrule outlines.
Individuals
and fragments
available.
The
price is between US
$6.40 and
US
$9.50 per
gram according to the weight of the piece.
Pour convertir le prix en Euros, cliquez sur
le lien ci-dessous :
See
more items: 
price: