July 13-22, 2005: Blue Forest, Wyoming and Salmon River, Idaho

One of many trip reports by Alan Silverstein.
Last update: March 12, 2008

From:  Alan Silverstein <ajs@frii.com>
Date:  27 Jul 2005 12:48:10 -0600
Subject:  (FC Rockhounds) Blue Forest last week
To:  fcrhc@yahoogroups.com (Fort Collins Rockhounds Club)

Howdy gang. I'm back from a major adventure and still digging out; thought I'd tell you about the rock-related part of my travels.

On the way to Salmon, Idaho on Wednesday, July 13, I camped on the BLM land east of Big Sandy Reservoir -- southwest Wyoming, 9 miles north and 2 east of Farson, which is about 40 miles north of Rock Springs. I hunted for a few hours that evening at many stops along the two-track roads east of the reservoir. Most spots offered some scattered wood chips, but very little blue agate. However, about six miles east of the reservoir on the north fork of the road, right in the road, I found one nice chunk of fossil cane with some blue. High clearance is a good idea, but 4WD was not required.

This area hasn't changed noticeably since I first visited around 1996. Best scavenging was at the old digs about a mile east of the fork on the south road; didn't have time before dark to go further east.

I rafted the main Salmon River for five nights from Corn Creek to Diamond Spring, about 95 river miles across most of the narrow "neck" of Idaho from east to west. This section is mostly Idaho Batholith, meaning lots of granite, schist, and gneiss, and not much else. Toward the end of the week I saw one small chunk of chalcedony in a gravel bar, and a little boring jasper. I noticed that the rock here makes lovely off-white sandy beaches with sparkly mica, and the river is very clear and green -- there's no mud, and the silt does not stay suspended. Wish I'd known to bring a mask and snorkel!

After flying back from Lewiston, Idaho to Idaho Falls on Thursday, July 21, and stopping into Lava Hot Springs (southeast Idaho), I camped for the night on top of a bluff, on a rough two-tracker road, a couple miles south of the main collecting area of Blue Forest. This is between Kemmerer and Farson, about 12 miles west of the paved road north to Farson. ("Eden Valley" wood occurs in many locations over a vast area many miles across.)

There were old digs on the bluff and I found a little good material, small pieces weathered down the hills, but again, not much blue agate. In the morning I enjoyed prospecting along the two-tracker north to the main gravel road again, then went north through the main area of Blue Forest to a separate small bluff a couple of miles away that Don Eastman had told me about in 1996 and identified as a "prime location". The whole area, again, hadn't changed much since my first visit over ten years ago, except there were a lot more oil or gas wells in the neighborhood, and a few more side roads. Still no identifying signs or any official BLM notice regarding Blue Forest wood itself; it's very low-key.

Don was right about that hill! The top was thick with old diggings, and the scavenging was great, lots of nice wood and lots of blue agate. I brought a shovel, but being short on time, with the hot weather, and lots of good surface scavenging available, I didn't do much digging. I explored the edge of the bluff counter-clockwise, then walked around the base once clockwise, with lot of ups and downs both ways.

This bluff makes the local geology a lot clearer. The wood occurs in a relatively narrow band of brittle, tan/brown, glassy shale that sits atop a thicker formation of crumbly blue shaley mudstone, above simpler mudstone with some (uninteresting) alluvial stones in it, which forms lower badlands. If you don't want to dig, which is hard work and chancy, it's fun to hunt the hillsides below the brown shale for naturally eroded pieces.

Below the northwest side of the bluff I found a gorgeous, blue-coated limb section about 1.5" in diameter and 3-4" long, a classic specimen. It's the kind of fossil that people dig for through the hard shale on top. This one must have weathered out long ago, somehow survived fracturing into chips, and sat there in plain sight for many years. I'll bring it to the September meeting. Most of what I found were fragments, some in cast/matrix.

After about six hours hunting in the Blue Forest area on July 22, I continued to Saratoga for a shower and fast swim in the very hot spring. North of town the county road I know about had weathered a little more, and I gathered another quart or so of small, gemmy petrified wood pieces. Ironically the club was heading to the same area the next day, but I wanted to get home Friday night.