Obsidian comes from volcanoes, not from a single region
Obsidian is a glassy volcanic rock, and its geological sources are scattered across many parts of the world rather than concentrated in one place [4]. The published list of source regions runs from Mediterranean islands and southeastern Europe through Anatolia and the Middle East, East Africa, northeast Asia and Japan, the islands of Southeast Asia, Oceania and the Pacific, and along the mountain chains of western North America and the Andes of South America [4]. In other words, if a region has had the right kind of volcanic activity, it may host obsidian.
Individual sources can be quite localized. In the Philippines, one known source group is at Nagcarlan in northern Luzon, and a more recently identified potential source sits in the Municipality of San Fernando on Mindanao — described as a secondary source found along the banks of the Lugawon River in Bukidnon, central Mindanao [1]. In North America, the Wagontire source lies in central Oregon [2]. These are the kinds of specific places geologists and archaeologists pinpoint when they trace where a piece of obsidian originally came from.
The stone is often found far from the volcano that made it
Where obsidian is found is not only a geological question. People have used it to make stone tools for two million years, and its uniqueness led to distribution or trade over hundreds and even thousands of kilometers [4]. So an obsidian artifact in an archaeological site may sit a long way from any volcanic source.
A striking example comes from beneath Lake Huron, where two obsidian flakes were attributed to the Wagontire source in central Oregon — a distance of more than 4,000 km — and dated to roughly 9,000 years ago, making them the earliest and most distant reported occurrence of obsidian in eastern North America [2]. In the Philippines, Mindanao obsidian shares a similar geochemical source group with Bukit Tengkorak in Sabah, Malaysia, and Leang Tuwo Mane'e in Talaud, Indonesia, which the authors read as indicating long-distance mobility across the Celebes region [1]. These are interpretations of movement, not proof of a single route, but they show how far the material can travel from its origin.
How a piece of obsidian is traced back to a place
Obsidian carries a chemical "fingerprint" that can be used to identify its source, which is why provenance studies are possible at all [1]. Researchers compare the chemistry of an artifact with the chemistry of known geological sources. In the Mindanao work, 259 obsidian artifacts from archaeological sites were analyzed with portable X-ray fluorescence spectroscopy and, as expected, matched the known San Fernando source [1]. Portable X-ray fluorescence instruments have greatly increased the number of artifacts that can be studied, including in museum collections [4].
Along the upper Columbia River valley, 27 archaeological sites yielded 545 obsidian artifacts, and 82 of them were sent for X-ray fluorescence geochemical analysis [3]. That study found that selective conditions favored non-local, high-quality obsidian sources across most object types and reduction classes, and that source diversity appears to increase over time and space [3]. The pattern is about which sources people chose and how that changed, not about a single deposit's location.
A source's location matters, but so does how people used it
Knowing where obsidian can be found does not tell you how a particular community used it. In Aotearoa New Zealand, Māori discovered and used a range of obsidian sources, and analysis of seven North Island assemblages dating to the Early/Middle period (AD 1250–1600) and the Late period (after AD 1600) documented a shift in the type of economization — from conserving material to maximize its use toward maximizing the number of artifacts [5]. The authors speculate this may be due to population increase and decreased direct access to raw material, though reuse and post-depositional damage are compounding factors that remain underdetermined [5].
The broader point is that obsidian's distribution changed over time in different regions, and analyses in the western Mediterranean, the Near East and Latin America have revealed distribution patterns that shifted over time, which researchers infer reflects developing socioeconomic complexity [4]. So the answer to "where is obsidian found" has two layers: the geological sources, which are fixed, and the archaeological occurrences, which reflect where people carried, traded and discarded the stone.
Sources used in this answer
Geochemical characterization of obsidian from the island of Mindanao, Philippines
Obsidian from Mindanao, Philippines, matches a potential secondary geological source at San Fernando along the Lugawon River in Bukidnon, and shares a geochemical source group with sites in Sabah, Malaysia, and Talaud, Indonesia.
Central Oregon obsidian from a submerged early Holocene archaeological site beneath Lake Huron
Two obsidian flakes from a submerged site beneath Lake Huron were traced to the Wagontire source in central Oregon, more than 4,000 km away, dating to about 9,000 BP.
Obsidian Occurrence and Frequency from the Upper Middle and Lower Upper Columbia River
In the upper Columbia River valley, 27 archaeological sites contained 545 obsidian artifacts, and analysis indicated selective conditions favored non-local, high-quality obsidian sources, with source diversity increasing over time and space.
Obsidian in Prehistory
Geological obsidian sources have been identified in many parts of the world, including Mediterranean islands, southeastern Europe, Anatolia and the Middle East, East Africa, northeast Asia and Japan, island Southeast Asia, Oceania and the Pacific, and western North America and the Andes.
Temporal patterns in the economization of obsidian use in Aotearoa New Zealand
Māori used a range of obsidian sources across Aotearoa New Zealand, and analysis of seven North Island assemblages documents a shift over time in the type of economization of obsidian.