Collecting minerals can be a fun hobby, in part because there are so many different types of minerals to identify. There are many tests you can perform without the need for special equipment to narrow down the possible identity of a mineral. The descriptions of common minerals in this article can also help you compare results. You can even skip the first part of this article and go straight to the description to find out certain things without needing to do any testing first. For example, mineral descriptions will help you distinguish gold from other shiny yellow minerals; study the shiny, colorful striped pattern on a rock; or identify a unique mineral that peels off into sheets when you rub it.
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Part 1 of 2: Doing the Test
Step 1. Distinguish minerals and rocks
Minerals are combinations of chemical elements in certain structures that occur naturally. While a mineral can appear in various shapes and colors as a result of geological processes or in very small amounts of impurities, in general each mineral sample will have certain characteristics that you can test. Rocks, on the other hand, can form from a combination of minerals, and have no crystalline structure. Minerals and rocks are not always easy to distinguish. However, if this test yields different results in one part of the object than in another, the object is likely rock.
You can also try to identify the rock, or at least try to identify the rock type
Step 2. Understand mineral identification
There are thousands of minerals on earth, but many of them are rare, or can only be found deep underground. Sometimes, you just need to do two or three tests to narrow down the possible object you want to know about to one of the common mineral types listed in the next section. If your mineral characteristics don't match any of the descriptions below, try searching for mineral identification guides in your area. If you've done a lot of testing, but can't narrow down the possible mineral types to two or more, look online for photos of similar minerals and specific tips for distinguishing them.
Including at least one test that involves a physical examination such as a hardness test or scratch test is the best option. Tests that only look at and describe a mineral may not be very useful, because different people may describe a mineral in different ways
Step 3. Check the shape and structure of the mineral surface
The general shape of each mineral crystal and the pattern of a group of crystals is called habit. There are many technical terms used by geologists to describe the shape and structure of minerals, but a basic description usually suffices. For example, is the mineral wavy or smooth? Is the mineral composed of rectangular crystals that overlap each other. or pointed crystals pointing out?
Step 4. Notice the glow or shimmer of your minerals
Sparkle is a mineral's way of reflecting light, and while this is not a scientific test, it is often useful to include a mineral's luster in its description. Most minerals have a "metallic" or "glassy" luster. You can also describe the mineral's luster as "oily", "pearl-like" (a white luster), "earth-like" (dull, like unglazed earthenware), or any other description that fits your mind. Use some adjectives if you need to.
Step 5. Pay attention to the color of the mineral
For most people, this is the easiest test to do, but it's not always helpful. Even a small amount of other compounds in a mineral can cause it to change color. So, one type of mineral can have a variety of colors. However, if the mineral has a unique color, such as purple, this color might help you to narrow down the possibilities.
When describing minerals, avoid colors that are difficult to describe, such as "salmon color" and "coral". Use simple terms like "red," "black," and "green."
Step 6. Perform a scratch test
This test is an easy and useful method, as long as you have white porcelain without a glossy finish. The back of a kitchen or bathroom tile might work for you; try to buy one at the building shop. Once the porcelain is available, rub the mineral over the surface, and look at the color of the "scratch" it leaves. Oftentimes, these streaks are a different color than the piece of mineral you're holding.
- Use porcelain that doesn't have a glossy finish. The non-glossy coating does not reflect light.
- Keep in mind that some minerals won't scratch, especially hard ones (because they're harder than porcelain tiles).
Step 7. Perform a mineral hardness test
Geologists often use the Mohs hardness scale, which is named after the discoverer, to quickly estimate the hardness of a mineral. If you pass the "4" hardness test but fail the "5" hardness test, your mineral hardness scale is between 4 and 5, and you can stop testing. Try to make permanent scratches using these common minerals (or minerals found in the hardness tester), starting from the lowest to the highest, if successful:
- 1 -- Easily scratched with nails, feels greasy and soft (or can be scratched with talc)
- 2 -- Can be scratched using nails (gypsum)
- 3 -- Can be cut with a knife or nails easily, can be scratched with a coin (calcite)
- 4 -- Can be scratched with a knife easily (flourite)
- 5 -- Can be scratched with a knife, but hard; can be scratched using glass (apatite)
- 6 -- Can be scratched with a steel file; can scratch glass, but hard (orthoclase)
- 7 -- Can scratch steel files, can scratch glass easily (quartz)
- 8 -- Can scratch (topaz)
- 9 -- Can scratch almost anything, can cut glass (corundum)
- 10 -- Can scratch or cut almost anything (diamonds)
Step 8. Break the mineral and look at the fracture
Because a mineral has a special structure, it will fracture in a unique way. If the fracture occurs on one or more flat surfaces, the mineral shows "cleavage". If there is no flat surface on the fractured mineral, it is curved or wavy, the mineral has a "fracture".
- Cleavage can be described in greater detail based on the number of flat surfaces that created the fault (usually between one and four), and whether the mineral surface is "perfect" (smooth), or "imperfect" (rough).
- Mineral fractures have several types. Describe it as cracked (or "stringy"), sharp and jagged, bowl-shaped (conchoidal), or neither (uneven).
Step 9. Do another test if your mineral is still not identified
There are many tests performed by geologists to identify a mineral. It's just that many of the money tests are of no use to minerals in general, or may require special equipment or hazardous materials. Here's a brief description of some of the tests you might be interested in trying:
- If your mineral is attached to a magnet, it is most likely magnetite, the only common mineral with strong magnetism. If the attraction is weak, or the description of magnetite doesn't match your mineral, it's likely pyrrhotite, franklinite, or ilmenite.
- Some minerals melt easily in a candle or match flame, while others will not melt even when burned over high heat. Minerals that melt easily have a higher "melting power" than other minerals that are more difficult to melt.
- Some minerals have a distinctive taste. For example, rock salt (halite) has a salt-like taste. However, when trying a stone taste like this, do not immediately lick it. Wet your finger, rub it over the surface of the rock sample, then lick your finger.
- If your mineral has a distinctive smell, try to describe it and search online for a mineral that has that smell. Strong-smelling minerals are rare, although bright yellow sulfur minerals can react and produce an odor similar to rotting eggs.
Part 2 of 2: Identifying Common Minerals
Step 1. Read the previous section if you don't understand a description
The descriptions below use a variety of terms and numbers to describe their shape, hardness, appearance after fracture, or other characteristics. If you don't really understand what this means, read the section above for an explanation of mineral testing.
Step 2. The most common crystalline mineral is quartz. Quartz is a very common mineral, and its shiny or crystalline appearance attracts many collectors. Quartz's hardness is 7 on the Mohs scale, and it has all types of fractures when fractured, never giving a cleavage flat fracture. Quartz leaves no obvious streaks on white porcelain. The luster is glassy, or glossy.
Milky Quartz transparent, rose quartz pink, and amethyst purple.
Step 3. A hard, shiny mineral without crystals may be another type of quartz, called "chert"
All types of quartz are crystalline minerals, but some are called "cryptocrystalline," which are crystals that are so small that the eye cannot see them. If a mineral has a hardness of 7, fracture, and a glassy luster, it is probably a type of quartz called chert. This mineral is most commonly found in brown or gray.
"Flint" is one type of chert, but is classed in many different ways. For example, some people may refer to black chert as flint, while others simply call it flint if the mineral emits a certain luster or is found with certain rocks
Step 4. A mineral with a striped pattern is usually a type of chalcedony. Chalcedony is formed from a mixture of quartz and another mineral, moganite. There are many types of minerals with beautiful striped patterns. The following are two of the most common:
- Onyx is a type of chalcedony that has a pattern of parallel lines. The color is often black or white, but can also be other colors.
- Agate has a wavy striped pattern, and can be found in a variety of different colors. This mineral is formed from pure quartz, chalcedony, or other similar minerals.
Step 5. See if your mineral has characteristics that match feldspar. In addition to various types of quartz, feldspar It is also a mineral that is found in abundance. It has a hardness of 6 on the Mohs scale, leaves streaks of white, and can be found in a variety of colors and lusters. The fault forms two flat hemispheres, with a fairly smooth surface, and almost at right angles to each other.
Step 6. If the mineral peels off when rubbed, it's probably mica
This mineral can be identified easily because it peels off into thin sheets, which are flexible when scratched by a fingernail or even when rubbed with a finger. Muscovite mica or white mica is light brown or colorless, while biotite mica or black mica dark brown or black, with streaks of brown-grey.
Step 7. Know the difference between gold and fake gold. Pyrite, which is often thought of as gold, has a metallic yellow color, but some tests can distinguish it from real gold. Its hardness is 6 or more, while gold is much softer, with a hardness between 2 and 3. This mineral leaves a greenish-black streak, and can be crushed into a powder with sufficient pressure.
Marcasite is another mineral similar to pyrite. Meanwhile, pyrite crystal is shaped like a cube, marcasite is needle-shaped.
Step 8. Green and blue minerals are often malachite or azurite. Both of these minerals contain copper, as well as other minerals. Copper gives malachite a dark green color, while azurite turns blue. These two minerals are often found together, and have a hardness between 3 and 4.
Step 9. Use a website or mineral guide to identify other minerals
Your area-specific mineral guide will provide a description of the minerals found in that particular area. If you're having trouble identifying a mineral, try online sources, such as minerals.net, to look up your test results and match them against possible minerals.
