Indochinite is the regional name for tektites recovered from mainland Southeast Asia, principally from Thailand, Laos, Cambodia and Vietnam, and forming the Indochinese sector of the Australasian tektite strewn field. The Australasian field is the youngest of the four recognised tektite strewn fields on Earth and is dated to approximately 790,000 years before present. It is also by far the largest, covering roughly ten percent of the Earth's surface and including material recovered from Tasmania (Tasmanites and Australites) through Indonesia (Javanites and Billitonites), the Philippines (Philippinites), and continental Southeast Asia (Indochinites and Mongolianites at the northern extreme), with significant occurrences extending across the southern Indian Ocean and into the Antarctic region.

Origin and dating

Tektites are the natural glasses produced by hypervelocity impact events when a large meteorite strikes the Earth, melting and ejecting silica-rich target rock that is then thrown across vast distances and quenches into glass during atmospheric flight. The Australasian event is the most recent major tektite-producing impact, and the source crater has been the subject of long debate. The most widely accepted current proposal, supported by gravity-anomaly mapping, isotope geochemistry, and the distribution and age pattern of recovered material, places the source crater under volcanic cover in the Bolaven Plateau region of southern Laos. This proposal, advanced by Sieh, Herrin and Sieh in 2020 and corroborated by subsequent work, identifies a crater approximately 13 kilometres in diameter buried beneath young basalt flows. Earlier hypotheses placed the source in the Gulf of Tonkin or in the South China Sea; the Bolaven Plateau identification is now the consensus view.

The dating, originally established by potassium-argon and fission-track methods on tektites and confirmed by argon-argon dating, sits at approximately 790,000 years before present, coincident with the Brunhes-Matuyama geomagnetic reversal. This temporal coincidence has been the subject of speculation about possible causal links between major impact events and geomagnetic reversals, though the consensus view treats this as a coincidence rather than a causal relationship.

Physical and chemical characteristics

Indochinite tektites are typically black to very dark brown in transmitted light and opaque to nearly opaque in larger pieces. Surface morphology is highly characteristic: indochinites display ablation sculpting from atmospheric flight, including grooves, pits, flow lines and aerodynamic shaping, that distinguishes them from terrestrial volcanic glasses. Surface erosion since deposition has modified these features in many specimens, and a high proportion of recovered indochinites show pitting and weathering grooves that overprint the original ablation features.

Chemically, indochinites are silica-rich glasses with SiO2 contents typically 70 to 75 percent, with significant Al2O3 (10 to 15 percent), FeO and Fe2O3 (4 to 6 percent), MgO, CaO, K2O and Na2O. The trace-element pattern is the diagnostic signature: the Australasian tektites collectively share a target-rock fingerprint that ties them to a specific terrestrial sedimentary source rather than to a volcanic or extraterrestrial origin. Water content is extremely low, distinguishing tektites from volcanic obsidian, and the absence of microcrystalline phases distinguishes them from other natural glasses.

Refractive index for indochinite typically falls in the range 1.49 to 1.53, specific gravity around 2.30 to 2.45, and Mohs hardness around 5 to 6.5. The species is anisotropic in optical behaviour only where strain birefringence is present; the underlying glass is amorphous and isotropic.

Forms and morphology

Indochinite morphology spans a wide range of forms, including:

• Splash forms: spheres, drops, dumbbells, teardrops, discs and ellipsoids produced by surface tension during the molten phase. These forms are common in the Indochinese material, particularly in the smaller size classes (under 30 grams).
• Layered or muong nong type: large irregular blocks (sometimes referred to as "layered tektites" or "Muong Nong-type" after the Laotian locality where they were first systematically described) that show internal layering, lower-velocity ablation features, and chemistry distinct from the splash-form material in trace elements. These represent material that retained more residual heat and traveled less far from the source crater.
• Aerodynamic forms: button-shaped indochinites with rim and flange features produced by re-entry from suborbital flight, paralleling the more famous "button australites" recovered in southern Australia.
• Fragmented or weathered forms: many recovered indochinites are fragments of larger original objects, modified by post-depositional weathering during the 790,000 years since arrival.

Sizes range from less than one gram to several kilogrammes for the larger Muong Nong-type specimens. The largest documented Muong Nong-type pieces approach 20 kilogrammes.

Localities and recovery

Indochinite recovery localities are distributed across the central and southern provinces of Thailand, the Bolaven Plateau and surrounding region of southern Laos (including the Muong Nong type locality), eastern Cambodia, and southern Vietnam. The Khorat Plateau of northeastern Thailand has been a particularly productive recovery zone for splash-form material. Recovery is typically by surface collection in agricultural fields and along eroded riverbanks where weathering has exposed buried specimens, supplemented in recent decades by deliberate searching by collectors and small-scale traders.

The recovery economy supports a network of local collectors, regional traders, and international wholesalers, with the largest concentration of dealing centred on the gem-trade hubs of Bangkok and Chanthaburi in Thailand. Specimens regularly enter the international trade through these channels and are sold by mineralogical and meteorite-specialty dealers worldwide.

Use in jewellery and decorative work

Indochinite is cut and used in jewellery on a moderate scale. Cabochons, beads, faceted stones, and mounted natural specimens all appear in commercial production. The dark, near-opaque body colour limits the role of faceting; faceted indochinites can produce dark mirror-like reflections from internal surfaces but do not display the fire and brilliance of higher-RI transparent stones. Natural-shape mountings, in which a recognisable splash form is set in a wire or bezel surround, are popular among collectors who value the meteoritic origin and the distinctive morphology of individual specimens.

The market sits within the broader collector and mineral-specimen segment rather than within mainstream gemmology. Pricing for cut and cabochon indochinite is modest at the trade level, with prices generally well below those of moldavite (the European member of the tektite family from the Czech Republic and Germany, which trades at a substantial premium because of its translucent green colour and its considerably smaller supply). Premiums attach to specimens with intact aerodynamic features, to large Muong Nong-type pieces with minimal damage, and to documented finds from named localities.

Distinguishing indochinite from imitations and related materials

The principal natural look-alikes for indochinite are obsidian and other volcanic glasses, which have higher water content, often show microcrystalline inclusions on close examination, and lack the characteristic aerodynamic surface features of true tektites. Specific gravity overlap exists between indochinite and some obsidian samples, but trace-element analysis, refractive-index measurement, and inclusion examination on a careful examination by a competent gemmologist or laboratory readily distinguishes the two.

Glass imitations of indochinite occur but are uncommon because the species itself is sufficiently affordable that imitation is not commercially attractive. Where imitations exist, they are typically modern manufactured glass with surface texturing intended to suggest pitting and ablation; close examination reveals regularity and casting marks inconsistent with natural tektite morphology. The international meteorite trade has standards and reputable dealers (the International Meteorite Collectors Association, dealers including Robert Haag, Aerolite Meteorites, and a number of established traders in Bangkok) through which authenticated indochinite specimens flow.

Scientific significance

Beyond its decorative use, indochinite is of considerable scientific interest because it represents direct sampled material from an Earth-impact event of intermediate scale and recent date. Studies of indochinite chemistry, dating, distribution and morphology have informed the understanding of impact processes, ejecta dispersion, and the relationship between impact events and other Earth-system processes. The indochinite literature includes substantial work in journals including Meteoritics & Planetary Science, Geochimica et Cosmochimica Acta, and Earth and Planetary Science Letters, and the species is well-represented in major meteorite collections including those of the Smithsonian Institution and the Natural History Museum London.