Tektites, in the simplest
terms are pieces of natural glass. Several natural glass
types are found on the Earth. By outward appearance some
tektites resemble obsidian the commonest of the natural
glasses. Microscopically, tektites resemble glass more than
obsidian in that they are almost completely devoid of any
mineral crystals in their composition. The tektite glass is
homogeneous in nature with the elements it contains
dissolved and mixed. Tektites have much less water in their
composition than obsidians (often a thousand times less).
Also obsidians when heated will foam from the gases and
water they contain and this is one method of
tektite testing. At the same temperature tektite glass
may produce a few gentle bubbles. Tektites are made of a
glass which melts at a far higher temperature and it is far
more viscous.
Where did tektites come
from? There have been several schools of thought over the
last hundred years, but basically today it distills down to
the Earth through the impact of a meteorite or comet.
Tektites are fun to collect and websites that have
tektites for sale can also be a good source of
images.
In a cratering event, soil
and rock are liquefied, or vaporized. There is question as
to how long the tektites took to form and how high they were
ejected. Was it a simple trajectory or did they travel high
nearly into space? It is clear that part of the time they
traveled at very high speed for they had to traverse great
distances.
The Australasian strewnfield is thousands of
kilometers across. It is thought by impact theorists that
they are shaped in a plastic state as they spin. Later there
may be some mostly minor shaping by ablation. In regard to
the Australites, it is clear from
cross sectional analysis
that they are a remelted object. Unlike the other tektites
they received a major part of their final shape by ablation.
However, the button portion of the posterior side has
internal flow lines unchanged by remelting while those on
the incoming ablated side are turned an pulled. Clearly, the
internal structure was established and set, before the
hypersonic ablation in the atmosphere.
Current chemical analysis
of tektites indicates that there is a relationship to rocks
only found on Earth. Fifteen rare earth elements have been
used to show that their relative abundances are in exact
relationship to their abundance in tektites. Including an
anomaly in the amount of Europium. This depletion of
Europium is connected to calcium and CO2 chemistry on the
Earth. This depletion is exactly recorded in tektite glass.
Melting a granite like rock will essentially make tektite
glass composition. Oversimplification but actually close
since many sedimentary rock thought to be used for tektites
are derived from granites.
Tektites are found
sometimes as irregular blobs and angular fragments, but
often they are clearly a splash form of one type or another.
These splash forms include, spheres, discs, rods, teardrops,
dumbbells, and varieties of all these with bending and
slumping. Some of the forms listed are clearly a result of
the exaggeration of the cause processes of another form. For
example teardrops are by all appearances the result of the
continued separation of the bulbed ends of dumbbells which
have become too thin in the middle to stay connected.
Careful examination of the thin pointed end of an undamaged
teardrop will reveal that it has the same fine texture as
the rest of the piece and is not the result of breakage. It
has become a complete individual. The discs will often have
a cavity in the middle of each side causing them to be
thinner in cross section in the middle. On a much smaller
percentage of the
discs there will be a peak where they have
also spun off of another portion.
Spheres may have a smooth
surface or the pieces may be deeply grooved. The spheres are
also amongst the most stressed of the
tektites often
shattering into dozens of pieces when an attempt is made to
cut
tektites. Besides nearly perfect spheres they occur in the
whole spectrum of flatten and elongated round forms.
The dumbbells as the name
implies have knobs at each end connected by a middle which
is thinner. The rod forms are similar to the dumbbells in
size but have neither the thick knobs nor the thinner
middle. They are just rods with usually rounded ends.
Some of these forms will
show a slight ridge on occasion indicating ablation, but the
Australites are the real aerodynamic shaped tektites. In
their case ablation has done much to give them their form.
Australite buttons have a hemispherical side often showing a
spiraling raised line. The technical name for this is "ring
wave'' it is a
featured created as the surface melted,
partly burned away, and partly re-deposited in the flange.
The flange of Australite buttons is a ring of material
around the original core that builds up but does not
completely weld itself to the original mass. On occasion the
entire forward facing side and flange will detach leaving a
distinctive core. These flangless cores are found also.
Australites come in elongated forms as well as round.
Tektites come in many sizes
however, complete splashform types fall in the range of from
one inch to four inches. Their weight in the 10 to 100 gram
range. (Please excuse the generalizations, this is for the
readers who have not seen them and have no idea of the
exceptions that the tektite enthusiast will be familiar
with.) They can be much smaller and much larger than the
figures above, but for a simple average the range given may
be useful.
Tektites are not usually
smooth, they are usually pitted or grooved or a combination
of both. More often than not they have a bald spot which is
smooth. Many attempts have been made to explain the pitting.
It has been thought to be from exposure to chemicals in the
ground. Another explanation is that it is part of their form
received before landing, perhaps during flight in the
atmosphere. The inside of broken bubbles will often be
shinny showing almost no etching, yet it has been exposed to
the same chemicals for the entire time the tektite has been
on earth. The back un-ablated side of
Australites will often
be textured and old looking while the ablated front surface
and both surfaces of the flange will appear very fresh.
Again the time spent in the ground was of course the same.
The mechanism of texturing may be a process called spallation. Pieces of glass pop out of the surface coming
through the atmosphere. Some experimentation has confirmed
this as a possibility.
Tektites have been found
with other artifacts in archaeological sites dating back
thousands of years. They have a long history of use and
significance to man. Ancient man in many places
took advantage of the glassy nature of tektites and used
them for making flaked tools. Later, they were considered to
have religious significance in Asia, the colorful green
varieties (Moldavites) of Europe have been used for jewelry
for hundreds of years and are making a return as gems today.
Tektites are not found
everywhere on the Earth. They are found in strewnfields;
which are areas where the material has fallen upon the
ground and the material is confined to the boundaries of the
strewnfield. Tektites are found more or less randomly within
the strewnfield. In the case of meteorite strewnfields the
heavier fragments will be found at the farthest travel end
of the dispersion ellipse.
In addition to the large
forms found on the land,
microtektites are recovered in
cores of sediments taken from the oceans. This data helps to
define the boundaries of the strewnfields in the areas
covered by ocean waters.
There are four well
established strewnfields on the Earth and some other
locations where tektite glass or very similar glass is
found. The strewnfields are the North American (Georgia and
Bediasite Tektites), The Moldavite, which is really two small strewnfield close to
each other in Europe, The Ivory Coast, and The Australasian.
Debate continues as to
whether tektites are found on the same spot where they fell,
or whether they have been transported. Many scientists
insist that they are found close to where they fell because
studies indicate being glass they break very fast in a river
or stream or flood situation. Others strive to prove that
they have been worked from other strata and redeposited.
It is however clear in some
cases that they are found in essentially the spot they fell
and in a specific layer or horizon in the ground.
By far the largest; the
Australasian tektite area encompasses most of Southeast
Asia, including Vietnam, Thailand, Southern China, Laos and
Cambodia. It stretches across the ocean to include the
islands of the Philippines, Indonesia, Malaya and Java. It
reaches far out into the Indian Ocean and south to the
western side of Australia. Approximately one tenth of the
Earth's surface is accounted part of the strewnfield.
Australites are generally
very dark in color, for the most part essentially black.
Thin edges or broken parts will have a yellow or brown color
when examined with back lighting. They have a wide range of
forms. Teardrops, dumbbells, spheres, rods, discs and all
types of irregular shapes. In Australia are found
aerodynamic button shaped tektites and their cores that
remain when they fly apart in the passage through the
atmosphere.
The southeastern portion of
the United States has two regions where tektites are found.
The tektites from each location are quite distinct from each
other. Texas is the area where the
The
The western coast of Africa
is the location of the
