Protect Your Find: Three Lab Tests to Tell Tektite From Obsidian
Tektites form in seconds from meteorite impacts and carry almost no water, while obsidian forms slowly from cooling lava and holds measurably more moisture and internal crystals. The fastest field check is surface sculpture: tektites show aerodynamic pitting or flanged shapes from their flight through the atmosphere, while obsidian shows conchoidal fractures and flow-banding. Provenance is the second clue. A tektite belongs to a known strewnfield; obsidian belongs to a volcano.
TL;DR:
- Tektites are characterized by aerodynamic pitting and flanged shapes, while obsidian shows smooth conchoidal fractures and flow-banding patterns.
- Water content in tektites averages about 0.012 percent, which remains the key chemical marker distinguishing them from obsidian.
- Tektites originate from specific strewnfields linked to impact events, whereas obsidian forms near volcanic activity worldwide in contact with groundwater.
- Field tests such as surface sculpture, weight, and UV analysis can reliably differentiate tektites from obsidian before resorting to lab confirmation.
- Provenance and accurate testing are essential, as misidentification and misleading sourcing can inflate obsidian’s value to imitate tektites.
Table of Contents
- Tektite vs obsidian: a quick ID checklist
- The science behind the identification
- Strewnfields versus volcanic belts: where each one comes from
- Practical tests: field checks first, lab work second
- Buying and collecting: provenance, value, and red flags
- How Legacy Crystals and Minerals documents natural glass specimens
- Obsidian specimens worth adding to a collection
- Sources
- FAQ
Tektite vs obsidian: a quick ID checklist
Before you reach for a loupe, check the basics. Most misidentifications happen because two visually similar glasses get compared without a system.
- Surface texture: Tektites often show pitting, grooves, or the flanged, button-like shape typical of australite specimens. Obsidian shows smooth conchoidal fractures and sometimes swirling flow-bands.
- Colour and clarity: Tektites are usually black, olive, or dark green and opaque in mass. Obsidian ranges further, including the golden sheen sometimes seen in tumbled specimens.
- Internal structure: Obsidian often contains visible microlites or tiny crystal inclusions under magnification. Tektites are typically featureless glass, sometimes with schlieren (streak) patterns.
- Size and weight: Most tektites run about 1 cm to a few centimetres and feel light for their size. Obsidian pieces vary widely, from pebble-sized chunks to large volcanic blocks.
- Common lookalikes: Slag glass, man-made glass, and dark basalt get mistaken for both. None of these belong in either category.
Statistic to anchor your checklist: measured tektite water content averages roughly 0.012±0.004 weight percent, a figure so low it separates tektites from nearly every other natural glass, including obsidian.
The science behind the identification
The water content gap is not a minor technical detail. It is the clearest chemical fingerprint separating these two materials, and it traces back to how each one formed.
Tektites form when a meteorite strikes Earth with enough force to melt surrounding rock and eject it into the atmosphere, sometimes past the edge of space, before it cools into glass. That process happens in near-vacuum conditions, which is why tektites end up with such low water content compared to other glasses. Obsidian, by contrast, cools from molten lava at the surface, in contact with the atmosphere and groundwater the entire time, which lets more moisture and microlites work their way into the structure.
That formation difference shows up under magnification, too. Obsidian commonly contains microlites and shows flow-banding from its slow volcanic cooling, while tektites are typically clean glass, occasionally interrupted by lechatelierite, a rare silica glass created only by the extreme heat and pressure of impact events.
If you want lab-level confirmation, three methods do the heavy lifting — explore the best crystals for emotional healing to support your wellness journey. Infrared spectroscopy measures water content directly. UV-vis-NIR spectroscopy detects water-related absorption bands around 1,380 and 2,210 to 2,250 nanometres, present in obsidian and largely absent in tektites. Standard petrographic microscopy reveals microlites and lechatelierite that the naked eye misses entirely.
Strewnfields versus volcanic belts: where each one comes from
Tektites do not show up randomly. They cluster in a handful of named strewnfields, including the Australasian field (the largest, spanning parts of Asia and Australia), the Ivory Coast field, the Czechoslovakian field that produces moldavite, and the North American field centred on Texas and Georgia. Specimens from these fields typically run about 1 cm, with some specimens reaching several centimetres in size.
Obsidian follows a completely different distribution pattern. It forms wherever felsic lava cools quickly at the surface, which means it shows up near active or historically active volcanoes worldwide, from the Pacific Northwest to Iceland to the Mediterranean. Obsidian is a silica-rich volcanic glass, roughly 65 to 80 percent silica, and it has been common enough historically that ancient toolmakers relied on it constantly. If a seller claims a specimen came from “a volcanic region” rather than a documented strewnfield, you are very likely looking at obsidian, not a tektite.
Practical tests: field checks first, lab work second
Work through these steps in order, saving the most invasive options for last.
- Loupe inspection. Look for pitting, flow-banding, and microlites under 10x magnification. This alone resolves most cases.
- Heft and size check. Weigh the specimen against its apparent volume. Tektites feel notably light; obsidian feels denser for comparable size.
- UV or visible-light comparison. Some sellers and labs use UV-vis-NIR readings to check for water-related bands invisible to the eye.
- Send for infrared analysis if provenance is unclear and the specimen has real value. This is the only test that gives you a hard water-content number.
One historical test deserves a warning rather than a recommendation. Heating a specimen with a blowpipe or torch causes obsidian to froth into pumice-like foam, while tektites fuse with far fewer bubbles. It works, but heated tektites frequently shatter on cooling from thermal stress. Never do this to a specimen you care about.
Pro Tip: When you photograph surface sculpture for remote identification help, use raking light from one side rather than a direct flash. Shadows across pits and grooves show up far better than flat, front-lit shots, which tend to wash out the exact texture an experienced eye needs to see.
Buying and collecting: provenance, value, and red flags
Documentation matters more with natural glass than with almost any other collectible mineral, because visual mimicry between tektite and obsidian is genuinely easy to fake or misjudge.
- Ask which strewnfield the specimen is assigned to, and expect a specific answer, not “found overseas.”
- Request find-site photos or documentation tying the piece to a known locality.
- For higher-value pieces, ask whether infrared or spectroscopic testing has been done, and by whom.
- Compare the asking price against typical moldavite and tektite market values, since named varieties carry real premiums that ordinary obsidian should not.
Watch for red flags: vague origin stories, specimens that look suspiciously uniform (a sign of tumbled obsidian sold as raw tektite), and sellers who resist providing extra photos or basic testing. Obsidian is common and inexpensive relative to verified tektites, so a seller pricing plain obsidian as though it carries strewnfield provenance is either mistaken or misleading you.
How Legacy Crystals and Minerals documents natural glass specimens
Legacy Crystals and Minerals sources museum-grade specimens with documented provenance rather than vague “natural glass” labelling. Founder Simon built the brand’s educational content, including detailed breakdowns of moldavite verification, around the same identification principles collectors need at the point of purchase: origin, testing, and honest labelling.
When you buy from a reputable seller, expect three things at minimum: a clear statement of geological origin (strewnfield or volcanic locality), photos that show surface texture in enough detail to check for pitting or flow-banding, and straightforward answers when you ask how a piece was identified. Legacy Crystals and Minerals also covers related identification questions, including how to tell natural crystals from synthetic ones, for collectors building out a broader specimen library.
Obsidian specimens worth adding to a collection
If your research points you toward obsidian rather than tektite, at least you are buying a material with a documented volcanic origin and no ambiguity about what it is. Several retailers offer obsidian across formats built for different collecting goals.
The Premium Black Obsidian Egg 2in. is intuitively selected and polished for display, a good fit if you want a finished piece that shows obsidian’s glassy lustre without any raw edges. For collectors who prefer to study the material in its natural state, Raw Black Obsidian Chunks show conchoidal fracture patterns exactly as they broke from the parent flow, with no cutting or shaping involved. If you want something wearable, the Golden Obsidian Tumbled Stone in A Grade brings a sheen that plain black obsidian does not have, and it works well set into jewellery or added to a curated display.
Specimens often include sourcing information to inform buyers about their geological origin. Browse the full raw minerals and crystals collection or check the museum quality minerals and crystals selection to compare documented specimens side by side before you buy.
Sources
- Tektites
- Infrared analysis of water in tektites and other glasses. - ADS
- Tektites
- Tektite gemstone information - Gem Society
FAQ
How can you tell if a rock is a tektite?
Check for aerodynamic surface pitting or a flanged, button-like shape, then look for the absence of microlites and flow-banding under magnification, since tektites are typically clean glass with occasional lechatelierite. Confirming origin against a known strewnfield, such as the Australasian or Czechoslovakian fields, gives the strongest proof.
Are tektites worth anything?
Named varieties like moldavite carry real market value tied to documented provenance and rarity, while unverified or common fragments are worth far less. Value depends heavily on size, clarity, shape, and confirmed strewnfield origin rather than the material alone.
Is obsidian the strongest stone?
No. Obsidian is a hard, glassy volcanic rock that fractures easily along sharp conchoidal lines, which made it useful for ancient cutting tools but also makes it brittle rather than tough.
Who should not wear black obsidian?
There is no scientific safety concern with wearing black obsidian, since it is chemically inert and used widely in jewellery, including pieces from the Golden Obsidian Tumbled Stone line. Anyone with a specific metaphysical or personal sensitivity to certain stones should follow their own judgment, since that guidance is a matter of individual practice rather than geology.
