No. 64 - Jul-Aug 1989
Libyan Desert Glass weighing as much as 16 pounds are found in an
oval area measuring approximately 130 by 53 kilometers.
pieces are concentrated in sand-free corridors between north-south dune
ridges. The origin of this immense deposit of glass has been attributed by
some to ancient nuclear explosions and alien activities, but investigating
scientists have always been satisfied with a meteor-impact hypothesis.
recent study (abstract below) also opts for this explanation, although no
one has found a crater of suitable size or other supporting evidence.
Libyan Desert Glass (LDG) represents 1.4 x 109 g of natural glass fragments
scattered over about 6500 km2 of the western Desert of Egypt. We made a
systematic study (employing INAA, microprobe and mass spectrometry
techniques) of several varieties of LDG and locally associated sand and
sandstone to provide insight into the nature and formation of these
enigmatic glass fragments.
These studies indicate that:
Although the LDG has restricted major element compositions (97.98 wt% SiO2 ;
1-2 wt % Al2 O3 ) their trace element contents (ppm) (Fe, 490-5200; Co,
0.2-1.2; Cr, 1.2-29 and Sc. 0.462.5) vary by as much as a factor of 5 to 30
The LDG fragments exhibit a factor of three variation in the REE abundances
(La, 5.4-15.3 ppm). They all show parallel and steep LREE enriched patterns
([La/Sm]N , 3.8-4.2) and flat HREE ([Tb/Lu]N , 1.1- 1.2) and distinct
negative europium anomalies (Eu/Eu*, about 0.5)
The gases in the vesicles of
LDG (N2 , Ar, O2 , CO2 , H2 O and their
dissociation products) are present in proportions consistent with derivation
from the terrestrial atmosphere
Dark streaks present in some samples of
LDG contain significantly higher
siderophile element abundances (Ir, about 0.5 ppb), possibly representing a
"Our studies suggest that
LDG is the product of meteorite impact into quartz-rich
surficial eolion and alluvial sand, and perhaps also into quartz-rich
sandstone, of the western Desert of Egypt."
(Murall, A.V., et al; Eos, 70: 379, 1989.)