Club home | 1999 Field Trip Reports

Arkansas has three official state rocks and minerals, all named by the legislature in 1967, and two more that every Ouachita rockhound should know. This is the page I wish I'd had when I started. It's written for beginners and for kids, so the geologists in the club will find things to correct, and are welcome to.

Quartz is silicon and oxygen, the most common mineral at the surface of the earth. Most of it is in sand and in rocks, and doesn't look like anything. But in the Ouachita Mountains, hot water carrying dissolved silica worked its way into cracks in the rock a very long time ago, and as it cooled, the quartz grew into crystals, some of them water-clear and as long as your arm. Arkansas quartz is known all over the world for its clarity, and people in the business will tell you there are few places like it.

How to know it: six sides, coming to a point, like a pencil sharpened with six flat cuts. It will scratch glass, and a knife won't scratch it. It breaks in curved, shell-like surfaces, not flat ones.

Words you'll hear: a point is a single crystal. A cluster is a group grown together on a base. A double-terminated point has a point on both ends, because it grew loose in clay instead of attached to rock. A phantom has the ghost of an earlier, smaller crystal inside it.

Where to find it: the fee mines in the Ouachitas, where you pay by the day to dig. It's the best way for a beginner to go. See our March trip for what a day of digging is like, and how to clean what you find.

Diamond is pure carbon, crushed into a crystal deep in the earth's mantle and carried up in a volcanic eruption. In Arkansas that eruption happened something like a hundred million years ago, and what's left of the volcano's pipe is now a field at Crater of Diamonds State Park, the only place in the world I know of where the public can pay a small fee, hunt for diamonds in the original rock, and keep what they find. It's been a state park since 1972.

The largest diamond ever found in the United States came out of that field: the Uncle Sam, 40.23 carats, found in 1924, before it was a park. Most diamonds found there now are small, from a fraction of a carat to a carat or two, and they come in white, yellow and brown.

How to know it: it doesn't look like a jewelry store diamond. A rough Arkansas diamond is usually small, rounded, with smooth curved faces and a bright, greasy-looking shine, like a tiny drop of glass that's been tumbled. Dirt doesn't stick to it. The park staff will identify anything you find, free, and weigh and record the diamonds.

Tips: go the day after a hard rain and walk the rows looking for a shine on the surface. Otherwise, dig and wet-sift, and flip your screen over to look at the middle, where the heavy stones settle. Bring a lunch, a hat, and more patience than you think you need. See our May trip.

Bauxite is the ore of aluminum, a reddish-brown or tan rock that formed where older rocks weathered for a very long time in a warm, wet climate, until most everything washed out but the aluminum. It's often full of little round pellets, like dried peas stuck in clay. Arkansas had the richest bauxite deposits in the country, in the low hills between here and Little Rock, and mined nearly all the bauxite produced in the United States. During World War II a great deal of it went into airplanes. There's even a town named for it.

How to know it: earthy, red-brown, often with those round pellets, and lighter in the hand than you'd expect. It doesn't look like much. It's the most important rock in this state's history anyway. Ask any of our older members whose fathers worked the mines.

This is my favorite, and the most Ouachita rock there is. Novaculite is a very dense, very fine-grained rock made almost entirely of microscopic quartz. It's white, gray or cream, sometimes stained pink or black, with a waxy look, and it breaks with an edge as sharp as glass. The name comes from the Latin word for a razor.

Two things made it famous. First, it's the stone the Arkansas whetstones are cut from, the finest natural sharpening stones in America, in grades from softer and coarser to hard and fine. Second, the native people of this country quarried it for thousands of years for knives, scrapers and arrow points, and Ouachita novaculite has been found at sites far from here, carried by trade.

How to know it: hard enough to scratch glass, very smooth on a broken face, often with a slightly translucent edge if you hold a thin piece to the light. It makes ridges in the Ouachitas because it's harder than the rocks around it, so the softer stuff wore away and left it standing. See our April trip.

Wavellite is an aluminum phosphate mineral, and it's the prettiest thing you'll find in the Ouachitas that most people have never heard of. It grows in thin, needle-like crystals that radiate out from a center, so on the face of a broken rock it looks like little green or yellow-green circles, pinwheels or starbursts, anywhere from the size of a pencil eraser to a half dollar. Break one of the round ones in half and you'll see the needles fanning out like the spokes of a wheel.

It's named for an English doctor who found it in the 1700s in England, but some of the finest specimens anywhere come from the Ouachitas. It forms in cracks in the shale and chert here. Most of the good localities are on private land, so permission is everything. We're going after some on Saturday, November 13.

How to know it: green to yellow-green, glassy, in round radiating sprays on a flat rock surface. Soft enough that a knife will scratch it, so be careful cleaning it.

What to get started with: a rock hammer (a real one, not a claw hammer), safety glasses, gloves, a hand lens (10 power), a streak plate (an unglazed white tile), a cheap pocketknife for hardness tests, a notebook, newspaper for wrapping, and egg cartons for the small stuff. And a good field guide from the library. Then come to a meeting, and we'll take you out.