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Meteorite Impact Glass: Tektites, Moldavite and Fakes

November 4, 2026 / 9 min read / By Viral Tandel

Somebody hands you a chunk of bottle-green glass with a wrinkly, almost carved surface and says it came from space. Or you spot a black, glassy blob in a tray at a gem show, labeled "tektite." Both are real things with a wild backstory, but neither is quite what the label suggests.

What is meteorite impact glass?

When a big asteroid slams into Earth, the ground and the incoming object try to occupy the same space at the same instant. The American Museum of Natural History describes the result as an explosion: some of the surface rock is not just thrown into the air but heated into a melt that behaves like liquid glass.

Geologists call everything made this way impactites: melted rock, shocked minerals, shatter cones and more. The glassy members of that family are what collectors call impact glass. Some of it stays near the crater. Some of it flies a very long way.

Here is the key point for anyone hoping they found a space rock: impact glass is made of terrestrial rock, rock that was already on Earth. So impact glass is a souvenir of an impact, not a piece of the thing that hit.

How do tektites form?

Tektites are the long-distance travelers. The AMNH calls them "splash droplets" from major impacts: blobs of melt that fly through the atmosphere and quench into solid glass, often keeping a droplet shape. The area where they come down is called a strewn field, and it can stretch for hundreds or even thousands of miles.

A University of Waterloo explainer lists the classic tektite shapes: buttons, dumbbells, teardrops, disks and rods, ranging from sand-grain size up to about 1 kilogram (2 pounds). Not every tektite is a neat splash form, though. Researchers describe Muong Nong-type tektites from Southeast Asia as the least streamlined and the largest of the ejected melt fragments: blocky, layered chunks rather than droplets.

Which kinds of impact glass are most famous?

Three names cover most of what you will see for sale. Ages and sources come from the museum, gem lab and journal pages listed at the end of this post.

A few details worth knowing about each:

• Moldavite is green because it contains very little iron. GIA notes that all other tektites are richer in iron and therefore black. The National Museum in Prague holds the largest public moldavite collection in the world, with specimens from about 140 find sites in Bohemia and Moravia.
• Australasian tektites come from what a 2020 study in the Proceedings of the National Academy of Sciences calls the largest known young meteorite impact on Earth. The authors propose that the source is a crater about 15 km (9 miles) wide, buried under younger lava flows in southern Laos.
• Libyan Desert Glass had a long-debated origin. In 2019, a Curtin University team reported tiny zircon grains in the glass carrying evidence of reidite, a high-pressure mineral that forms only in meteorite impacts. The same glass was carved into the scarab on one of Tutankhamun's pectorals.

Is impact glass a meteorite?

No, and that is not a technicality. A meteorite is a piece of an asteroid (or, rarely, of the Moon or Mars) that fell to Earth. Washington University in St. Louis (WUSTL) puts it plainly for moldavite: it is glassy impact ejecta made of terrestrial material that melted and cooled quickly in the atmosphere, so it is not a meteorite, although it is attractive. If the words meteor, meteoroid and meteorite blur together, our guide to meteor vs meteorite sorts them out.

That also means the usual meteorite clues point the other way. Very few meteorites have gas bubbles, while glass often does. WUSTL notes that glass fractures conchoidally (in smooth, shell-shaped curves) and that a rock with conchoidal fractures is not a meteorite. For the whole checklist, see our guide on how to identify a meteorite.

Black tektites can also be confused with volcanic glass and with slag, the glassy waste from smelting. Our guides to obsidian and rocks that look like glass cover those look-alikes, and meteorite or meteorwrong covers slag. Shape helps: a true splash form (button, teardrop, dumbbell) is a good sign of a tektite, but a lab is the only way to be sure.

Why is so much cheap moldavite fake?

Because demand is high and green glass is cheap. A 2015 report in GIA's journal, Gems & Gemology, noted that moldavite prices had risen and that imitations had become more widespread as a result. Imitations are not new, either. Faceted moldavite was popular in Czech jewelry in the second half of the 1800s, and imitations made from green bottle glass appeared by the early 1900s. When a GIA contributor examined five 19th-century "moldavite" jewelry sets in a Prague museum, only one set actually contained moldavite, so glass fakes are even older than people thought.

Modern fakes are better. The same GIA report describes small imitations from China, just a few grams each, whose wrinkled surface was likely created by etching glass in acid. WUSTL adds that many fake "tektites" sold online are plain glass, and that some offered as moldavite look "a bit too perfect and regular in shape."

Price is a useful sanity check. As of September 2026, Aerolite Meteorites listed rough moldavite at roughly $20 to $30 a gram (for example, a 1.4 g piece for $35), while black Indochinite tektites sold for well under $1 a gram (a 19.4 g piece for $6) and Libyan Desert Glass for about $2 to $3 a gram. These are one dealer's asking prices, not an appraisal. Still, a big, flawless "moldavite" at a small fraction of the going rate should make you suspicious.

How can you spot fake moldavite?

GIA published a side-by-side comparison of natural moldavite and imitations. Here are the clues that matter most:

What you can check at home

1. Use a 10x loupe. Look inside for plenty of round and stretched bubbles and for thin, curving wires. GIA notes that dunking rough material in water (or oil) makes the lechatelierite easier to see.
2. Check the density. Weigh the stone dry, then weigh it hanging in water from a thread. Divide the dry weight by the weight it lost in water. Natural moldavite comes out around 2.27 to 2.46.
3. Judge the size and shape. A fist-sized, perfectly symmetrical "moldavite" is a warning sign.
4. Ask where it came from. Good sellers name a find area. GIA notes that Besednice, in South Bohemia, is widely considered the source of the finest material.

Acid-etched fakes can copy the surface almost perfectly, and some imitations do not glow under UV either. If a lot of money is at stake, a gem lab can measure refractive index and absorption spectra, which GIA used to separate the real thing from the glass.

Can you collect impact glass yourself?

Only where the land manager allows it. The National Museum in Prague lists moldavite find sites that include working sand mines, and those belong to somebody. Wherever you are, the basic rules are the same:

• Private land: always get the owner's permission first.
• National parks (US): collecting any rocks or minerals is prohibited, and so is using a metal detector. Our guide to the meteorite metal detector covers where detecting is allowed.
• BLM land (US): reasonable amounts of rocks and mineral specimens for personal, noncommercial use, except in closed or posted areas. Ask the local BLM office.

The takeaway

Impact glass is a genuine piece of cosmic history, just not a piece of space. Tektites like moldavite are Earth rock melted by an impact and splashed across whole regions. If you are buying, look for bubbles and silica wires, check the density, be wary of perfect shapes and bargain prices, and remember that a gem lab has the final word. If you found something glassy and heavy and wonder what it is worth, our guide to meteorite value explains what actually drives prices. The RockhoundID app, coming soon, will suggest likely matches from a photo and tell you which test confirms them.

The pictures in this guide are AI-generated illustrations of what to look for; real specimens vary, so trust the tests over any picture. RockhoundID guides help you narrow down what you found. They suggest likely candidates, not certain identifications or appraisals. For anything valuable, rare or possibly from space, ask a museum, a university geology department or your state geological survey, and check the collecting rules for the land before you take anything home.