Rocks and minerals can be found everywhere, but there is a learning process involved. Some places are better than others, and it takes an advanced level of practice before you can find something interesting nearly anywhere. Here are some of the different levels of interest that people may have in rocks and minerals:
- The average grownup does not notice rocks unless they are in the way for some reason. These people tend to collect very few rocks, and those either as decoration or mementoes.
- The average child notices stones and admires their shapes and colors. Children tend to collect indiscriminately wherever they go, even where it is inappropriate or forbidden.
- The average rockhound usually seeks a few favored rocks or mineral classes as part of a hobby. Rockhounds tend to focus on approved mines, quarries and other recognized localities, and also rock shows and rock shops.
- The average professional geologist notices rocks everywhere, but thinks of them as means to an end. Geologists tend to examine a lot but collect very few rocks outside their narrow specialties, except maybe a pet rock or two.
- The average artisan, landscaper, artist or prospector notices rocks but with highly selective eyes. These people tend to acquire rocks only for specific useful purposes like jewelry, walls, sculpture or sources of economic minerals.
This article is for the beginning student of geology, who has a degree of the child's encompassing curiosity without the narrower interests of the other groups.
Hunting Rocks: Beaches and Riverbeds
For education, there is no substitute for examining as many different rocks as possible.
The child usually begins at the beach. Many beaches are full of rocks, and you'll never run out because they're spread across large areas and renewed with every tide. The ground is safe, biting insects are few and visibility is good. Sunscreen and water are your basic needs. Although many beaches are public parks, at which collecting is not allowed, no one will prosecute you for taking away a discreet pocketful of pebbles.
Beach rocks are generally clean and fresh from their grinding in the surf zone. That also means that beach rocks tend to be the harder rock types (igneous and metamorphic). It's not always easy to tell where a beach rock is from—it may derive from cliffs along the beach or a submerged offshore outcrop, it may have come down a river from far inland, and it may also have traveled some distance along shore due to wave action. Beach rocks, then, are stones without much context.
River rocks are much more likely to originate nearby and to include softer rock types. The farther upstream you can go, the truer this is. You'll want sturdy footwear, and you'll want an idea of whose land you're on.
Beaches and rivers are good places to start your rock education from scratch, or to make your first acquaintance with a region. For more serious study of rocks, though, you will need to find exposures of bedrock.
Bedrock: Exposures and Outcrops
Bedrock or living rock is intact rock that has not been broken from its original body. A place of any kind where bedrock is lying there ready for your hammer is called an exposure; a natural exposure is called an outcrop.
Exposures may be quite widespread, if you consider artificial ones. A building excavation can be found in any town, for instance. Mines and quarries can have excellent exposures, and they have the advantage of being more permanent than excavations. But in all of these cases, you will generally need the landowner's permission to investigate or collect rocks and minerals. Landowners have good reasons to say no and few reasons to say yes. Experienced, organized groups have the best shot, which is a good reason to join a club.
The best bedrock exposures are generally found in roadcuts, and amateurs and professionals alike rely on them heavily. Roadcuts have many good features:
- They're clean, especially when new
- They're easy to visit, alone or in a group
- They're public property, and hammering is generally not forbidden
- They expose rocks well, even soft rocks
- They expose rocks in their context, including features and structures not visible in a hand specimen
Roadcuts are off limits wherever parking is not permitted, like freeways. Railways are private property and should be avoided. And roadcuts in parks, whether national parks or local ones, should generally be visited with your hammer left in the car.
Outcrops may be found at the beach or the riverside, too—in many regions these are the only places to find them. For more, you need to visit the hills and the mountains. Most federal public lands, such as national forests, can be explored freely by amateurs.
Most parklands forbid defacing or removing any natural features—this means you. For all other lands, I suggest an approach that leaves the rocks looking no worse than you found them. Remember what every child knows: rocks are beautiful.
Hunting Minerals
You might say that minerals can be found wherever rocks are. That's a good starting point, but soon enough the mineral hunter learns better. Rocks like shale or basalt, for instance, generally have mineral grains that are too small to see with a magnifier. But even these rocks offer possibilities to those who know where to look.
Minerals grow in several main settings:
- Primary minerals form during the solidification of a melt.
- Evaporitic minerals form by precipitation out of concentrated solutions.
- Diagenetic minerals form at low and moderate temperatures during the consolidation of a rock from sediment.
- Vein minerals form during injection of deep hot fluids.
- Metamorphic minerals form in solid rocks under prolonged heat and pressure.
If you can recognize the signs of these settings, you can expect to find the typical minerals they give rise to. Even a plain-looking mudstone may have zones of alteration or veins in it, or partings that reveal mineral nodules that grew during diagenesis. In brief, the mineral hunter needs to know more geology than the rock hunter.
