SERPENTINE AT THE SPILLWAY?

Rex Burress

The front-page comment recently about the dam spillway was that asbestos had appeared in the earth mix. Asbestos, the widespread mineral sometimes associated with our official state rock, serpentine, has been detected, the news item stated.

When undisturbed, asbestos is relatively benign, even quite lovely, but the dust can be lodged in the lungs and cause trouble in excessive amounts...thus it was claimed after becoming our state rock in 1965. Now some actions have been taken to remove serpentine as California's symbolic stone. Not yet!

After the 1997 overflow flood, water was blasted down the spillway at 160,000cfs and devastated the opposite hillside. Soil and plants were ripped away right down to jagged bedrock. I explored that mountainside before, during, and after the powerful surge that sent a strong wind and mist up across the hill and the highway in a path of destruction. ( I kept a record, and within five years, 48 species of plants had returned.)

After the flood, I spent hours carefully clamoring over the tilted formations, marveling at the geological jumbles that resembled sculptures, and I noticed a two-inch seam of pure asbestos streaking through one section. The silken fibers gleamed in the sunlight and made a shimmering luster, quite harmless in the unusual occurrence if not crushed to dust. Perhaps there was a connection to serpentine although that slick green rock appears more commonly farther up the river. The combinations of minerals is what helps make rocks fascinating.

In my prime rock-hounding days, my gem-hunter's atlas mentioned agatized tremolite near Iowa Hill up toward Auburn. Tremolite, or California Tigereye, is a combination of serpentinized asbestos, as the siliceous solution solidified ages and ages hence into today's prized gem rock. A more massive example is the African Tigereye with its long, straight fibers as compared to the more convoluted CA variety.

I tracked the tigereye to the American River area and found a few pieces although it was intertwined with massive serpentine. There is a specimen of that tremolite in the Feather River Nature Center along with serpentine that you can see someday when the flood-damaged road is fixed.

Studies have been done on serpentine soil where only certain plants can grow due to lack of certain minerals, and stymied by an excess of chromium, cobalt, and nickel toxins.

There is a five-mile section of the Feather River Canyon through abundant serpentinite [a rock composed of several minerals of the serpentine group] and where there are often landslides of the beautiful though brittle rock onto Highway 70. The formation starts at the Rich Bar overlook where even the parking place shows excavated serpentine stone. Finding a piece for your rock collection is no problem and you might find samples of associated jade and chrysotile. In the F.R. Canyon at Mill Creek, I have also found soft talc in serpentinite that can be carved into soapstone ornaments.

Gold isn't generally found in serpentinite, but underneath the eroded boulders of Deep Canyon, a large amount of placer gold was taken out as described in the book, “Deep Gold.”

In the Bay Area hills, there is a serpentine ridge in Joaquin Miller Park where the poet built his funeral pyre and chiseled out a grave for his mother. More serpentine is found in California than any other state, mostly because of the close proximity to the ocean depths from whence peridotite was metamorphosed into serpentine at the tectonic plate junctions. Now didn't you want to know that!

“As long as I live, I'll hear waterfalls and birds and winds sing. I'll interpret the rocks,

learn the language of flood, storm, and the avalanche. I'll acquaint myself with the glaciers

and wild gardens, and get as near the heart of the world as I can.”--John Muir

“The very stones seem talkative, sympathetic, brotherly.”--John Muir