Why obsidian?
Obsidian sits at a useful intersection of ordinary observation and deeper geology. A hand specimen can show a glassy luster, flow banding, bubbles, pale inclusions, and curved fracture scars without specialist equipment. Those details lead naturally to questions about silica-rich lava, rapid cooling, crystallization, and the long human history of worked stone.
The notebook began in June 2026 with a short entry about reflected light along a broken edge. The archive is deliberately narrow: each note begins with something that can be seen in a photograph or on a specimen, then checks the interpretation against a public geological or museum source.
Working method
Observation and interpretation are kept separate. “A thin grey highlight appears along the edge” is an observation. “The curve records conchoidal fracture” is an interpretation, and should be supported by a reliable source. Locality information is not invented when a photographed specimen has no recorded provenance.
- Use soft, directional light and a neutral background.
- Record scale, visible texture, luster, and obvious weathering.
- Avoid destructive tests and never collect from protected land.
- Prefer USGS, National Park Service, museum, and original image records.
- Credit every photograph that was not made specifically for this site.
Editorial limits
The notes are educational summaries, not professional geological identifications. A photograph rarely establishes composition or locality by itself. Cultural objects are discussed only in general terms; archaeological context and collection law matter more than a visual resemblance.
Substantive corrections are folded into the relevant note with an updated review date. The Sources & image credits page records the references and licenses used throughout the archive.