More Resources

Rocks and Minerals

Discover Nature in the Rocks: Things to Know and Things to Do by Rebecca and Diana Lawton, and Susan Panttaja.

Field Guide and Introduction to the Geology and Chemistry of Rocks and Minerals by George F. Sandstrom

Rocks and Minerals by Chris Pellant. Smithonian field guide.

Field Guide to North American Rocks and Minerals by the National Audubon Society.

Note: Simon and Schuster and the Cambridge Press also publish field guides.

Understanding minerals and stones
Mineralszone.com

Rocks - An Introduction
ScienceViews.com

Mineral I.D. chart

Mineral classification

Mining and Ore Processing

Intro to ore extraction

Where to hunt for rocks and minerals
Desert USA

Prospecting for Minerals and Metals
MineralProspector.com

Prospecting for Gold by Harold Kirkemo, USGS

Extracting rock and mineral ores
Brittanica

Bowen's Reaction Series (PDF)
Skidmore College

Specific Gravity Table For Ceramics, Metals & Minerals
Reade

Primitive Technology and Native Arts

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Rock and Mineral Prospecting

Any long-term survival training should include techniques for mining and collecting ores and other useful minerals. A mineral is composed of either a single element (like gold) or compound of elements (like sodium chlorine - aka table salt). As a rule, minerals have a solid, crystalline form. Common ones used in construction or household products include quartz, talc, gypsum, graphite and sulphur. And the rocks that house these minerals may be useful in themselves, such as chert and obsidian for flintknapping, granite and marble for construction, etc. This section of the Mega-Disaster Planner provides a brief tutorial on the subject.

Rocks are created initially by magma (below the surface) or lava flowing above the surface of the earth. Rocks that solidify above the surface are known as extrusive (volcanic), while rocks that form below ground are called intrusive (or plutonic). Geologists further divide all rocks into three basic groups:

Minerals large enough to be visible to the naked eye were produced (in most cases)from magma that solidified below the Earth's surface. The farther down into the crust you go, the bigger the crystal size. That's because submerged minerals may take thousands of years to cool down. And thousands or millions of years after that, hydrothermal activity and plate tectonics push these rocks up above the surface. Half Dome and El Capitan are examples of this process. Many similar, light-colored intrusive rocks with visible minerals are termed granitic.

Over time, weathering, landslides and other forms of erosion peel or break down igneous rocks. Often they end up as rolling stones carried by rivers and creeks down to lower altitudes. Anyone who studies geology learns the habits of the different rock and mineral types, which makes locating and identifying important minerals a lot easier.

One of the scientific tools used to determine where different minerals end up is Bowen's Reaction Series. Experiments conducted a century ago showed that specific minerals crystallize at certain temperatures, or in concert with other minerals. And since the rare ones like gold form alongside more common minerals (such as quartz and copper), this intel greatly aids the work of prospecting around igneous rock formations.

While the diagram you see above may not seem like much help, rock charts based on the reaction series provide a roadmap for geologists seeking to decipher a particular terrain. As a rule, igneous rocks with minerals that crystallized at high temperatures are comparatively rich in magnesium and iron and are called mafic (magnesium + ferrous) igneous rocks. Rocks with minerals that crystallized at lower temperatures are rich in silica, sodium or potassium, and are called felsic (feldspar + silica) rocks . Between these two compositional extremes are andesitic rocks, which are found along the margins of continents, as in the case of their namesake, the Andes Mountains.

If this still sounds about as clear as mud, read the following briefing paper prepared by Brooklyn Collge. It will come in handy when you start boning up on the key minerals and rock types with practical uses in everyday life.

Rock Charts, Photos and Identification

Another natural process that affects rocks and minerals is chemical weathering. In particular, weathered feldspar minerals will degrade over time and give birth to clay minerals like kaolinite. From these deposits we get the material to make stoneware and other durable ceramics. Iron and other metals are likewise affected by chemical weathering, particularly their exposure to oxygen. Oxidation transforms the metals into a mineral group known as oxides.

In order to return them back to their pure metal state, the mineral and rock ores are smelted or heated in some other way. In our early history, charcoal and wood fires, and later cupolas or funaces built with refractory ceramic clay or bricks and used to create metals. (Refractory means that the material doesn't melt under high heat.) The idea is to generate a lot of carbon through burning, which replaces the oxygen in the metal oxide. In the case of iron, higher temperatures are needed to melt the ore, and that in turn generate enough carbon to makes the metal brittle. This lead our borbears to pour the molten iron into molds. That's how we came to have cast iron.

In order for a blacksmith to pound the metal into various shapes, a second processing step is needed to lower the carbon level in the iron. For more on iron and steel, see the next section, Blacksmithing .

Besides oxides, minerals may fall into one of several other groups, based on common elements shared (like oxygen or sulphur). They're known as sulfides, sulfates, carbonates, halides and silicates. Of these, the silicates comprise 90 percent of the earth's crust and are based on a combination of the elements silicon and oxygen. Quartz, feldspar and mica minerals are the best known and most prevalent of the silicates.

Around volcanoes and hydrothermal veins you'll find the native element sulfur, a yellowish substance that smells like rotten eggs but which has a multitude of uses, including as a pyrotechnic agent and medicine. For most of recorded history, sulphur was known as brimstone.

Sulfur

Granitic rocks, which are plentiful in the mountains, contain the silicate minerals feldspar, mica, quartz and hornblende. In contrast, limestone is made up of the remains of seashells and carbonate minerals like calcite. Limestone gives us lime, a popular building material since ancient times. Marble is a softer, metamorphized version of limestone, which makes it easier to carve. On the downside, marble degrades a lot faster than limestone and granite, so it's generally used indoors.

Mineral Identification

In order to identify minerals in rocks, geologists have developed an easy-to-learn classification system. It's based on observing or measuring the following characteristics:

Obviously you need to know a mineral's characteristics before you can identify it in the field. Amateur rock and gemstone hounds carry a rock and mineral field guide, which lists the specific traits of each classification. The job of making an I.D. is not a hard one, as it usually takes only a few telltale signs. Finding out the streak, for instance, narrows down the possibilities nearly tenfold. Of course, you may need to grind or chip into the rock that houses the mineral to reach a clean surface.

Unlike the streak, a mineral or rock's exterior color often tells you litte about the material, since all rocks are subject to chemical weathering and impurities. However, in igneous rocks a darker color usually indicates the presence of ferrous (i.e. iron-bearing) material, while a lighter color indicates potassium, calcium or sodium.

The rock's relative hardness can be deduced by scratching it against more familiar rocks or other materials whose hardness number you already know. If the unknown specimen scratches the familiar substance, then the specimen is harder. Glass, for instance, has a hardness of 5.5. A copper penny is 3, a pencil (graphite) is 1.5 and a finger nail about 2.5 on the scale. Unlike the pH or Richter scales, each Moh's hardness number doesn't represent a tenfold increase in hardness. It's only after the number 9 that the hardness level skyrockets. Thus the scale serves primarily as an aid to identification.

Stockpiling Key Materials

Hematite, which contains 65 percent iron oxide, is 6.5 on the hardness scale. It has a specific gravity of 5.26, no cleavage, uneven fracture, and has a submetallic luster. Its color may be red, gray, brown or black. Its streak is brownish red. Most often found in the vicinity of volcanoes and hydrothermal veins, hematite's major deposits in the U.S. were all exhausted by the end of World War II. Thus, finding iron domestically usually means a trip to the junkyard.

Here are some of the rocks, minerals and other other things to collect and stockpile should you find yourself dropping anchor in an untamed land:

Here's a mineral I.D. chart (PDF) to add to your survival notes.

Cinnabar

To learn the ropes of how to mine or collect minerals, gold prospecting may be the easiest avenue of exploration. Besides a ton of books written on the subject, you can download instructions on the internet for how to build sluice boxes and other contraptions used in extracting lode and placer (i.e. river) deposits. A prospector will dredge and pan creeks and riverbeds, search crevices in the bedrock along the shore, and poke around boulders to extract gold nuggets that get lodged there during the spring runoff from the mountains. Other essential tools of the trade include a rock hammer, mesh screen, tweezers and a jeweler's loupe, which is a compact magnifying glass you can carry in your shirt pocket.

Once a mineral deposit is located, the next task is to separate it from the surrounding rock and other minerals. Common processes include crushing, floatation, leaching and smelting. Chemicals like cyanide and hydrocloric acid are also used because the they cause the mineral to detach and collect. The trick is to know which mineral reacts with which chemical. Cyanide, for instance works well in separating gold, but with another metal you'll need something else. Historically, copper and iron have been extracted through the process of smelting, or cooking it up in a wood, charcoal or coke (i.e. cooked coal) furnace. Use the links in the gray box to the right to for more info on extraction and processing techniques.

To learn more about earth science in general, be sure to check out the standard textbook Earth Science by Tarbuck and Lutgens. It's well-written and many older editions exist, so you can buy a copy for less than $15. See Allbookstores.com for the latest prices. And don't forget to include a rock and mineral field guide with your survival gear. Make sure it's lightweight and includes color photos, the basic properties of each mineral and an explanation of its usefulness in everyday life. Some of these guides can be a little too comprehensive, since less than three dozen minerals are easily found in the earth's crust. (You can also probably do without the sections on fossils and gemstones.) If you're a minimalist, you can always cut out the relevant pages and stow them in a ziplock bag.

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