Saturday, July 30, 2011

A Visit to Mecca

Succor Creek Jasper

About two months ago I drove over to the Idaho/Oregon border to search for Owyhee Picture Jasper, one of the most spectacular in the world. It was my first time in the area, and I concentrated on the Succor Creek region SW of Homedale Idaho. Many people come here for Thundereggs, but I really wanted to find jasper - and I did.  However, because of heavy snows, the creek was still running too high to get across to some of the better jasper areas, so I concentrated my efforts in a few drainages coming out of the hills to the west.

My technique was simple, just wade up the still flowing stream, and look for things that looked interesting in the cold, clear water. I quickly trained my eye to spot the tan color of the jasper and filled my collecting bag in no time. And a second time, and a third time. Before I knew it, 9 hours had gone by and I had a car full of rock and an aching back!

Much of this jasper does not look like much in rough form; the colors and patterns are too subtle. But whenever you hit a rock and it breaks in conchoidal fractures (e.g. smooth glass-like flakes)  you know you're into jasper.

None of this was slabbing material : it was destined for my non-stop tumblers, which always have a series of rocks being polished. The small sample above, about 1.5" high, is one of my favorites. Not spectacular, but handsome enough that I enjoy having it, and many others like it.  Can't wait to go back.

Thursday, July 28, 2011

Mysteries on the Wild Coast

Seastacks, Olympic Peninsula
Good weather on the coast lured me out to one of my favorite rockhounding locations.  As in my "Conveyor Belt" post a few days ago, many of the rocks that end up on the beaches of the Olympic Peninsula have been dumped there by glaciers and the massive rivers that they spawned. Although most of the rocks that comprise the many dramatic seastacks on the coast are sedimentary, there are plenty of interesting rocks from somewhere else. Several areas on the Peninsula have thick strata of what could only be ancient river beds, with rounded water-transported rocks that are clearly not local.

I found some terrific rocks on this trip, the most intriguing is the one below, which displays a color pattern like nothing I have ever seen before. It is dense and hard, and should polish nicely. Jasper?

Colorful rock, Olympic coast

This is what rockhounding is for me : a constant treasure hunt, and a vehicle for discovery.

Saturday, July 23, 2011

Ventifacts

Ventifact, Wright Valley, Antarctica
In 1980, I worked for a season as a field assistant at McMurdo Station, Antarctica. Among my most memorable adventures during those 4 months - and there were many - was a visit to the "Dry Valleys", a series of remarkable ice-free canyons.  I joined a group of scientists doing some sampling in the saline ponds there - see photo below - but also just enjoyed exploring this weird, lunar landscape.

The floor of the canyon was littered with rock, of course, mostly basalt (dolerite) chunks from a series of sills high on the ridges on either side.  What really made them unique, however, was their having been carved by the incessant wind into smooth, graceful objects - sometimes referred to as "ventifacts" or wind-carved stones.  I grabbed a couple of these mini-sculptures but left thousands more...including some perfect stone pyramids 6 feet tall, as smooth as if made from polished granite.

This little pyramid is only about 4 inches tall, but you can see the smooth, polished surface and the faceting caused by sitting in the exact position in the prevailing winds for many decades, perhaps centuries.  I have carried it with me for the past 31 years since that trip, and it is one of my most treasured possessions.

This is a similar process, by the way, to the "Topoliths" in the post below, though this is much harder rock, and polished over much longer periods of time.

Wright Dry Valley, Antarctica 1980

Tuesday, July 19, 2011

Mystery Rocks

Mystery Rocks, Olympic Peninsula
I would love to figure out what these rocks are. I have found them repeatedly among the beach gravels of the northern Olympic Peninsula, along the Straits of Juan de Fuca, but have not managed to figure out where they are from - or what they are.  (I found them in many locations but they are especially abundant around the mouth of the Elwha River)

They are brittle but soft enough that they do not take a polish, despite the superficial resemblance to the Orbicular Jaspers (with red spots) found in the same region.  But the raised dots are odd, and I can't think what rock type these might represent.  Anyone recognize them? The matrix is grey-green and apparently crystalline, but whatever it is, it's a really distinctive rock.

No mineral value, of course, and no one is going to make jewelery from this material, but if there is a geologist out there that recognizes it, or where it outcrops, I'd love to hear about it....

POSTSCRIPT : One reader asked whether the blebs are just surface marks, e.g. barnacle scars, but I broke some open and the spots are distributed throughout the rock.

POSTSCRIPT TWO :  MYSTERY SOLVED 8/26 !  More on a later post...

Monday, July 18, 2011

"Topoliths"

"Topoliths" , Eroded shale, Falkland Islands
A few years we discovered a location in the Falkland Islands where the ground is littered with these wind-carved pebbles of shale/slate. Because of the layering, and the incessant wind, these stones erode into wonderful "topographic" shapes, akin to the contours of topographic maps. (I particularly like the "map" of California above, app. 4 inches long).  Because of their similarity to contour maps, we call them "topoliths."

We have dozens of these remarkable little stones.  Let us know if you'd be interested in having one.

The Conveyor Belt

Beach Cobbles, Lincoln Park, Seattle
One of the best rockhounding locations in the Pacific Northwest is so close...that I can see it from my house. Seriously, one of my favorite rock-hunting spots is along any of the cobble beaches along the shores of Puget Sound. You can never tell what you might find out there including a variety of jaspers, agates, petrified wood, and just some beautiful stones of unknown origin. In fact, almost all of the rocks are from somewhere else.  Why?  Because almost all are leftovers from the Ice Age, when a glacier 5000 feet thick carved Puget Sound, and, like a gigantic conveyor belt, carried rock from a hundred locations to the north and dumped them here.

I find this fascinating. Some of the rocks I pick up along the beach may have been plucked from an outcrop in British Columbia, or have fallen off a peak in the North Cascades.  There are igneous rocks, metamorphics, and, of course sedimentary rocks as well: to be honest, I have no idea what half of them are!  Here are just a few samples from the beaches here, mostly jaspers, and at least one petrified wood.

All in a Day's collection, Puget Sound
Where are they from?  Who knows? Yes, sometimes it's a little frustrating to find a real stunner on the beach, knowing that you probably won't see another one, and with no clue where it originated. (It is rare, in fact, to see two rocks that appear to have come from the same locality.)

Having said that, most are beautifully rounded, making tumbling a snap. No surprise: they've been getting tumbled in the ocean for 10,000 years!

Far, Far, Away

Polished beach pebbles, Chiloe Island, Chile
Yes, I know, this blog is supposedly about Pacific Northwest rockhounding, but it is also a chance to highlight some of the oddballs in my collection.  Last year, I spent 2 months working on the island of Chiloe in southern Chile. While there, I was told by locals - who knew about my interest in rocks - about a nearby beach with "beautiful stones." Intrigued, I had them take me there. It was a nondescript little bay, like many others along this ragged coast, but I did notice that the beach pebbles had a striking variety of patterns, and the smoothness and heft of silica-rich stone. I collected a few pockets-full (God, how I wish now that I had gotten more!) and brought them home to polish.

The six samples above show how wildly different the stones were, in patterns and colors, yet all had the same relative hardness, and shine. But none are recognizable as agate (no transparency) or jasper: some have what looks like sedimentary layering, while others have no linear structure at all.  Clearly there is something interesting going on in the geology of this bay, but I have not been able to find any references online.

If anyone can suggest what these rocks are, I will tell you where I found them. I only wish I had an excuse to go back...

Mystery Solved...

Brecciated Cherts, Channel Islands, CA
I collected these stones along the shore of Santa Cruz Island in California's Channel Islands last year. They were obviously silica-rich and took a nice polish, but were structurally all over the map: some were clearly banded like a conventional sedimentary rock, while others were fractured and chaotic.  I collected a dozen or so, but could not seem to find out what they were.

Then, recently, I struck up a conversation with a California geologist, who turns out to have done his PhD on the rocks of the Monterey Formation and immediately identified these as nice examples of brecciated cherts from the Monterey!   I still haven't figured out the exact mechanism of their formation, but they are pretty unusual in any case.

St. Kilda Oddity

 Granite/Dolerite Breccia, St. Kilda, Scotland

I collected this rock two years ago on the remote island of St. Kilda, off Western Scotland. It is about 9 inches long, about the size of an enormous russet potato.  I was stunned by the structure of the rock, composed of angular blocks of dolerite (Basalt) "floating" in a granite matrix. This was the largest one I could carry - but much of the island ( a World Heritage historical site) is made up of this stuff. No gem value, obviously, but just a wonderful piece of geology.

Welcome

Owyhee Jaspers, Succor Creek, Oregon 
I am starting this blog just to record details of my completely unprofessional hobby of rockhounding.  I studied geology at the University of Washington three decades ago, and have always been interested in the subject, but only recently have I started actively looking for rocks as objects of beauty and design.  No, I am not a jeweler, and so far have resisted the temptation to invest in cabbing equipment and expensive polishers. Instead, I prefer the naturalistic forms of tumbled stones, particularly jaspers in all of their astonishing varieties of color and pattern.  As my wife can testify, our house is increasingly filled with polished stones.

These jaspers were all collected in a small streambed off of Succor Creek in Eastern Oregon, one of the best rockhounding locations I've ever seen.  Walking in the water, where the true colors of the stones were better displayed, I quickly filled up my collecting bag, not once, not twice, but three times - all in less than half a mile. I couldn't stop myself!  By the end of the day, I was more physically exhausted than I have ever been,  having spent 12 straight hours bent at the waist. That's the true nature of obsession...

More to come.