Desert prospecting

Meteorites are rare, only 3500 kilos were found in Antarctica after 25 years of successive expeditions (US and Japanese). So, if you hope to find one, you must know some basic information.

You can prospect everywhere in the desert, but after awhile you will realize that these space rocks, which are falling anywhere on the planet cannot be found everywhere. Why?
As a small meteorite can impact the ground with speeds upwards of 300 km/h (190 miles/h), one can easily understand that in the majority of cases the stone makes a hole in the soil and disappears from view. You will have to wait a long time, several hundred years or more, before the erosion brings it to light. Erosion is not the same everywhere, that's why some places are better to find meteorites than other. Such places are called strewnfields.

How we are working
Each of our finds are classified by a laboratory in relation with the Meteoritical Society. The traceability of all our meteorites is total. They are referenced independently of any commercial value. Most of the discoveries in the Sahara desert are done on state lands and a representative specimen of rare finds are available for original countries. When we found the main impact of the CO3 carbonaceous chondrite, named Dar al Gani 749, we have kept the 25kg main mass for Libyan museum.

An identity card with the following information is available for each new meteorite :

official name given by the Nomenclature Committee classification of the laboratory coordinates of the find, longitude and latitude date of the discovery total known weight TKW and number of fragments weathering (W0 fresh to W6) percentage of fayalite (Fa%) and pyroxenes (Fs%) name of the laboratory which has done the work photo of the meteorite in situ two views of the main mass view of the interior with a cut to compare with others specimens additional information, like pairing click the image to enlarge

• lack of any vegetation that would otherwise impair a visual scan,
• a flat terrain with only a few black rocks,
• the possible effects of ablation.
  You can begin your search.

Imagine you are lucky enough to find your first meteorite. Now you can begin the most exciting part of the search.
There is more than 90 chances in a hundred that your specimen, whatever its size, comes from a multiple fall, fragmentation in the atmosphere being capable of producing several individuals which strike the earth inside an area called distribution ellipse. So when you find one you can expect find more around. Data collected on Dar al Gani strewnfield confirm this reckoning.

This reassembled find shows distinct faces. No doubt there are more specimens from this fall. But a distribution ellipse can be very long, three or more kilometers between two paired meteorites is common.

Every prospector in desert countries knows that such information is absolutely essential for working on distribution ellipses and strewnfields. Even though the Sahara covers 9,000,000 square kilometers, only a few percents of this is easy to prospect. Data accumulated on Dar al Gani show that nearly all the meteorites are associated with a particular distribution ellipse field. That means more material available for science and collectors if you can determine the trajectory of the fall.

With two points you have an axis. Our second find is two kilometers from the cairn. We add this information inside our GPS memory and have a virtual image of a probable trajectory. Now we can concentrate our prospecting on a 500 m wide line.

Always keep in mind that you are the first human to discover new ET material, and as a finder you must gather as much information as feasible. This behavior is consistent with an ethical approach to meteorite prospecting. This information will help in future studies and will contribute to the growing data base for a better understanding of the Saharan meteorite population.

In many countries, you can buy at mineral dealer shops black stones slightly magnetic without documentation. Encouraging and financing this business is dramatically harmful to science: the gathered samples have no localization, making strewnfield studies and recovery of paired specimens impossible. The Sahara is the only place in the world where such studies are possible.

see: Dar al Gani strewnfield

In Antarctica these studies are difficult due to ice flows.

At least twenty grams are required for meteorites higher than 100 grams or 20% of the mass for smaller meteorites
Laboratories need a type specimen archived for future studies and a thin section. It can take six months or more for a classification.

The lab will ask us to document our field data, such as location, circumstances of find. We do a complete reference card, even for a 50 gram ordinary chondrite. Try to do the same work on your sample, cut a 20 gram slice and send the slice ready for a thin section, the photos and all the information you have to the laboratory.
A list of institutions working on meteorites can be found at the end of the Meteoritical Bulletin.

Temporary identification
We use a temporary identification before the meteorite is definitely named. This ID# (e.g., a capital letter followed by a number) will only be used between us and the lab. Then, this temporary ID# will be replaced by the official name given by the Nomenclature Committee of the Meteoritical Society.
As below: our field ID# was M28, now it is Dar al Gani 608 forever.
Any ID# which leads to confuse people is to be avoided.

Specimen from Sahara with unknown location
Nobody can agree with such practices, especially when you know that good work can be done on the Saharan strewnfields.