Philippinite is the trade and collector name for tektite found in the Philippines, a member of the Australasian tektite strewnfield produced by a meteoritic impact event approximately 790,000 years ago. Like all tektites, philippinites are natural glasses born of the high-temperature melting and ejection of terrestrial material by hypervelocity impact; they are not of extraterrestrial origin in the sense of meteorites, but they are inseparable from the impact record. In gemmology and lapidary work, philippinite is a minor material, faceted and cabbed for collectors rather than carrying meaningful market presence.

Composition and form

Philippinite is a silica-rich glass containing roughly 70 to 80 per cent SiO₂, with aluminium and iron oxides making up most of the remainder, and minor amounts of magnesium, potassium, and calcium. Specimens are typically jet-black to very dark brown by reflected light and show a deep brown body colour in thin section. Surfaces are commonly pitted and grooved, the result of atmospheric ablation during high-velocity flight, and shapes include teardrops, dumbbells, spheres, and irregular fragments characteristic of plastic deformation in flight followed by partial breakage on landing.

Refractive index falls in the 1.48 to 1.51 range; specific gravity is around 2.40. Hardness is roughly 5 to 6. The material is non-fluorescent and shows no birefringence, consistent with its glassy, isotropic structure.

The Australasian strewnfield

Philippinites are part of the Australasian tektite strewnfield, the largest and youngest of the four major tektite distributions on Earth, covering parts of Australia (australites), Indochina (indochinites), southern China, and the Philippines. The source crater for the Australasian event has not been definitively located, though the leading candidate is buried beneath sediment in Indochina. The 790,000-year age is well established by argon-argon and fission-track dating of tektite samples from across the field.

Philippinites are recovered across the archipelago, with productive areas in Luzon — particularly the Pugad Babuy and Bulacan localities — and in Mindanao. Collecting has historically been by surface picking in agricultural and eroded terrain.

In the trade

Philippinite is faceted and cabbed in small quantities for tektite specialists and natural-glass collectors, and the better translucent black material can take a high polish. Compared with moldavite — the green Bohemian tektite that has commanded substantially higher prices because of its colour and rarity — philippinite remains a modest collector item. Faceted stones rarely exceed a few grams of finished weight, and most market activity is in rough specimens valued for their aerodynamic forms.

Identification

Tektites are most often confused with obsidian, which is volcanic glass rather than impact glass and is generally lower in silica and higher in water content. Tektites are essentially anhydrous, a key compositional distinction. The aerodynamic surface sculpture of well-preserved specimens — flow lines, regmaglypts, and ablation features — is highly diagnostic when present, although water-rolled and weathered specimens may have lost these clues.

Further reading

• GIA Gems & Gemology — tektite and natural glass articles
• International Gem Society — tektite reference
• ICA — natural glass and impact materials