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. But first let's review what kinds of people look at rocks and minerals, and what they look for:
- 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 they shouldn't collect.
- The average rockhound seeks a few favored rocks or mineral classes as part of a hobby. Rockhounds tend to visit 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 specialties, except maybe a pet rock or two.
- The average artisan, landscaper, artist or prospector sees rocks with highly selective eyes. These people tend to acquire rocks only to use for things like jewelry, walls, sculpture or sources of economic minerals.
This article is for the beginning student of geology, who has some of the child's encompassing curiosity without the narrower interests of the other groups. For learning, there is no substitute for examining as many different rocks as possible. Now, where do you find them?
Hunting Rocks: Beaches and Riverbeds
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, where collecting is not allowed, no one will prosecute you for discreetly taking away a 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 wave action may have carried it some distance along shore. 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 common, 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 anyone from defacing or removing any natural features—this includes rocks, and this includes 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.
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.