Treasure Map Japan: Rockhound

A map of candidate collecting spots across Japan — places where you may be able to pick up stones — selected by cross-checking geological data with published occurrence records. It covers 20 minerals and fossils, including placer gold, amber, jade, topaz, obsidian, and fossil shark teeth.

■ Feels like a treasure hunt, grounded in geology
• The candidates are not guesses. We cross-reference open data from the Geospatial Information Authority of Japan and the Geological Survey of Japan, AIST (geological maps, mineral deposit databases, elevation, geochemical maps) with occurrence records from the literature.
• Every spot shows the evidence for why it made the map: distance to the source rock, the nationwide percentile of its streambed geochemistry, even the terrain conditions.

■ Reading the map is simple
• Color = mineral, size = potential, shape = type of place
• Placer gold is shown as points; everything else as bands (stretches of river or beach). The display follows the physics of specific gravity.
• Solid line = a stretch confirmed as beach or gravel bar with data; dashed line = a candidate stretch to verify on site

■ Start free
• The free placer gold area (Usotannai, Hokkaido) and the Choshi shark tooth fossil pack cost nothing
• Also free: 26 hands-on facilities and officially sanctioned spots nationwide, plus a mineral field guide with identification tips

■ Made for the field
• All candidate data is built into the app. Locations, evidence, and trip logging work even with no signal.
• GPX export links up with hiking GPS apps
• Every spot shows an ease-of-access rating (distance from the road, slope)

■ Being honest with you
• This app is a map of candidates. It does not guarantee that you will find anything.
• Off-limits areas such as natural monuments are included too — clearly marked as no-collecting rather than hidden.
• Always check access and collecting rules for each location before you go.

Gold panning, rockhounding, beachcombing, fossil hunting — turn your weekend treasure hunt from a matter of luck into a search backed by evidence.