Short answer: Libyan desert glass is a pale yellow to yellow-green natural glass that is almost pure silica, scattered across several thousand square kilometers of dunes in western Egypt near the Libyan border, in the Great Sand Sea. It formed about 29 million years ago when desert sand melted at well over 3,000 F, and zircon grains in the glass show that a meteorite impact, not an airburst, did it. Real pieces are unusually light (SG about 2.21), inert under UV, and frosted by wind.
What is Libyan desert glass?
It is glass made by nature from sand. Most of it sits as loose pieces on the desert floor between dunes in the Great Sand Sea of western Egypt, close to the Libyan frontier, which explains the name. Pieces range from fingernail chips to fist-size lumps; the International Gem Society's tektite table lists Libyan desert glass from Egypt and Libya up to 4,500 grams, with a specific gravity of 2.21, a refractive index of 1.462, and a pale greenish yellow color.
Those two numbers are the heart of the identification. Both are low for a glass, because Libyan desert glass is close to pure silicon dioxide, with very little of the sodium, calcium, iron or lead that raise the density and refractive index of other glasses. Curtin University describes it as nearly pure silica, a canary yellow glass found over several thousand square kilometres in western Egypt.
Typical rough has three features you can see without tools:
- Color from very pale straw through lemon and honey yellow to faintly green, sometimes with milky or cloudy zones.
- A frosted skin. Millions of years of wind-driven sand have sandblasted the surfaces to a satin or pitted matte finish. Broken faces are glassy and show conchoidal fracture.
- Inclusions. Bubbles, wispy streaks and darker swirls are common in natural glass. Bubbles alone prove nothing either way.
How old is Libyan desert glass, and how did it form?
The glass is about 29 million years old. The question of how it formed was argued for nearly a century, and the answer only came in 2019.
There were two candidates. One was a meteorite striking the ground. The other was an airburst, in which an incoming body explodes in the atmosphere and the heat melts the surface below. Both can melt sand. Archaeology magazine reports that the glass formed when quartz melted at a temperature in excess of 3,000 degrees Fahrenheit, hotter than the inside of a volcano, so heat alone could not decide between them.
Pressure could. Live Science explains the difference in scale: airbursts produce shock waves of thousands of pascals in the air, while impacts drive shock waves of billions of pascals into the ground. Only the ground impact can make the high-pressure mineral reidite, a dense form of zircon.
Aaron Cavosie of Curtin University and colleagues, including Christian Koeberl of the Natural History Museum Vienna, went looking for it. Curtin's announcement says zircons in the glass preserve evidence of the former presence of reidite, and the study was published in the journal Geology. The zircon grains had been reidite during the impact and later reverted to ordinary zircon, keeping a crystal orientation that betrays their history. Cavosie told Live Science that previous models treated the glass as the product of a 100-megaton class airburst, and that this is not the case.
One loose end remains. No crater has been found. Archaeology magazine notes that it may lie beneath shifting dunes or may have eroded until it is no longer recognizable. The broader process of making glass by impact is covered in the impact glass guide.
Is Libyan desert glass a tektite?
It depends on whose definition you use, which is why sellers call it "Libyan gold tektite" while many researchers simply say impact glass.
The International Gem Society treats it as one of the tektite varieties alongside moldavite, Darwin glass and the black Asian tektites, and notes that all tektites occur in the strewn fields of meteorite impacts. The same source gives the typical tektite as roughly 75% silica, with a refractive index of 1.46 to 1.54 and a specific gravity from 2.21 up to 3.40. Libyan desert glass sits at the extreme low end of every range, because it is purer silica than any other member. In practice, the trade name is harmless as long as nobody uses it to imply the material is moldavite.
How it compares with the glasses it is confused with:
| Glass | Silica content | Specific gravity | Refractive index | Under UV |
|---|---|---|---|---|
| Libyan desert glass | Nearly pure silica | 2.21 | 1.462 | Inert |
| Tektites in general | About 75% | 2.21 to 3.40 | 1.46 to 1.54 | None in UV |
| Obsidian (volcanic) | About 66 to 72% | Typically 2.33 to 2.42 | 1.48 to 1.51 | Varies |
| Manufactured glass | Varies | 2.30 to 4.50 | 1.470 to 1.700 | Some glow strongly |
Obsidian figures are from the IGS obsidian guide; manufactured glass figures are from the IGS glass guide. The moldavite comparison is covered in its own planned page, moldavite vs Libyan desert glass.
What is the connection to Tutankhamun?
The best-known piece of Libyan desert glass is a carved scarab at the center of a pectoral from the tomb of Tutankhamun, now in the Egyptian Museum in Cairo. The IGS records that in 1996 the piece caught the eye of a mineralogist, and the yellow-green gem in the middle of the pectoral turned out to be Libyan desert glass. Archaeology magazine describes the same ornament as an elaborate pectoral with a central scarab carved from canary yellow Libyan Desert glass. The scarab is why the material is sometimes marketed with Egyptian imagery. It is also a reminder that people were collecting this glass from the desert more than three thousand years ago.
How do you spot fake Libyan desert glass?
The fakes are yellow manufactured glass, sometimes tumbled or acid-frosted to imitate a desert surface. The good news is that real Libyan desert glass is lighter and lower in refractive index than nearly any glass a factory makes, so the numbers do most of the work.
- Weigh it in water. Specific gravity is the strongest home test. Weigh the piece dry, then suspended in water on a thread, and divide the dry weight by the loss of weight. Real glass from the Great Sand Sea should come in close to 2.21. The IGS gives manufactured glass a specific gravity of 2.30 to 4.50, so a reading of 2.4 or more rules out Libyan desert glass. This works best on pieces over 10 grams; tiny chips give noisy results.
- Shine a UV torch on it. The IGS lists tektites as showing no luminescence under UV. Some yellow and yellow-green glass glows, and uranium glass in particular, which the IGS notes gets its green to yellow color from added uranium dioxide, fluoresces brightly. A piece that glows vivid green is not Libyan desert glass.
- Read the surface. Natural pieces have an uneven, sandblasted skin with pits and ridges, and fresh breaks are clean and glassy. Uniformly smooth tumbled shapes, mold seams, or perfectly even frosting all over suggest manufacture.
- Use a loupe on the inclusions. The IGS notes that manufactured glass usually shows swirl marks and round bubbles. Natural glass has bubbles too, so look at the overall picture rather than at one bubble.
- Test the refractive index if you can. On a gem refractometer, a polished face should read about 1.462. The IGS range for manufactured glass starts at 1.470.
- Check the price. Small rough pieces are not expensive, and sellers usually price by the gram. Look for consistency: frosted surfaces, natural shapes, and weights listed per piece.
What not to rely on: color names such as "gold" or "honey", origin stories, or certificates from unnamed labs. A specific gravity reading on a large piece beats all of them.
How should you care for it?
The IGS gives tektites a hardness of 5 to 6.5 and warns that their inclusions make steam and ultrasonic cleaning unwise; a soft brush, mild detergent and warm water are enough. Store rough pieces so their frosted skins do not grind against harder stones. Yellow natural glass does not fade in light, so display is unrestricted.
What does crystal tradition say?
In crystal traditions, Libyan desert glass is associated with the solar plexus, personal power and the sun, partly because of its color and its Egyptian connection. These are beliefs, not tested properties, and they have nothing to do with whether a piece is genuine.
What to look for when you buy Libyan desert glass
Buy on four points: color, clarity, surface and weight. Clear, evenly colored lemon to golden pieces with a natural frosted skin are the most sought after; cloudy or streaky pieces are cheaper and just as genuine. Ask for the weight of the exact piece, and for anything over about 10 grams, ask the seller for a specific gravity reading or do it yourself on arrival.
From the Market:
- Libyan desert glass, sold by the gram: rough pieces in 2.5 to 2.9 gram and 13 to 13.5 gram sizes. The larger size is big enough for a meaningful water-weighing test at home.
- Moldavite, 1 to 5 gram pieces and pendants: the green Central European tektite, useful side by side to see how differently two impact glasses look. The checks for moldavite are covered in the fake moldavite guide.
- Black obsidian sphere, 50 mm, 166 g: volcanic glass, the everyday natural glass. Weighed against its size, it shows the higher density of obsidian compared with the pure silica of desert glass.
Digital Towns Market
Libyan desert glass in stock
Frequently asked questions
How old is Libyan desert glass?
About 29 million years. Research led by Curtin University, published in the journal Geology in 2019, dated the melting event to that age and showed from former reidite in zircon grains that it was a meteorite impact rather than an atmospheric airburst.
Where is Libyan desert glass found?
In the Great Sand Sea of western Egypt, close to the Libyan border, where pieces lie on the desert surface between dunes across several thousand square kilometers. Despite the name, most of the strewn field is on the Egyptian side.
Is Libyan desert glass the same as moldavite?
No. Both are impact glasses, but moldavite is green and comes from the Ries impact in Central Europe about 15 million years ago, while Libyan desert glass is yellow, purer silica and about 29 million years old. Their specific gravity and color separate them easily.
Does real Libyan desert glass glow under UV?
It should not. The International Gem Society lists tektites as showing no luminescence under ultraviolet light. Some manufactured yellow glass, especially uranium glass, fluoresces bright green, so a strong glow is a reason to doubt the piece.
Why is it called Libyan gold tektite?
It is a trade name. The glass is yellow, it comes from the Libyan Desert region of the Sahara, and the International Gem Society classes it among the tektites. Many geologists simply call it impact glass. The name does not change what the material is.
Sources
- International Gem Society, Tektite Value, Price, and Jewelry Information: https://www.gemsociety.org/article/tektite-jewelry-and-gemstone-information/
- Curtin University, Curtin planetary scientist unravels mystery of Egyptian desert glass: https://www.curtin.edu.au/news/?p=19254
- Archaeology Magazine, Scarab From Space: https://archaeology.org/?p=8565
- Live Science, King Tut Wore Ancient, Meteor-Blasted Yellow Glass: https://livescience.com/65503-glass-egypt-desert-meteorite-impact.html
- International Gem Society, Obsidian Value, Price, and Jewelry Information: https://www.gemsociety.org/article/obsidian-jewelry-and-gemstone-information/
- International Gem Society, Glass Gemstones: https://www.gemsociety.org/article/glass