Millard County · west of Fillmore / south of Delta
Black Rock Desert obsidian
This is the common “Utah obsidian” walk. It is still not one color on the map.
Young volcanic ground between Delta and Fillmore sheds black, mahogany, and snowflake glass on the surface. Utah Geological Survey and BLM have talked about this field in public for years. That does not mean every acre around a stock tank is casual-use BLM.
This is also not the Modena source and not the Wild Horse Canyon quarry in the Mineral Mountains. Those are separate pages.
Status in one line
Much of the walked ground is BLM. School trust (SITLA) and private parcels sit in the same neighborhood — including numbered sections UGS has already flagged in print. Confirm the acre you park on and the acre you stoop on.
What UGS already put in public
The Survey’s Black Rock write-up is a status warning, not a treasure map: BLM around the public watering area, school trust on specific nearby sections, private ground at a historic mine area. Use current SITLA / BLM layers. Section numbers in an old pamphlet can lag a sale or a land exchange.
Collecting frame (typical casual use on open BLM)
- Personal use, not for sale
- Hand tools
- 25 lb/day + one piece, 250 lb/year
- Leave marked claims alone
- Fillmore Field Office / West Desert District for current postings
Glass vs artifacts
Surface cobbles on open BLM are a weight-cap problem. A point, core, or flake scatter is an artifact problem. Same rule as everywhere else on this site. See artifacts are not specimens.
What this site will not publish
No turn-by-turn from Hwy 257. No “walk east from the trough.” Buy a current printed guide if you need a starting pullout, then check ownership before the bucket comes out.
Before you go
- Ownership layer — BLM vs SITLA vs private vs claim.
- If it is SITLA, you need their rockhounding permit. BLM casual-use rules do not travel with you across the section line.
- Water and heat. This field looks close to pavement. It still cooks.
Informational only. Confirm with the BLM Fillmore Field Office and current SITLA maps before you collect.