Collecting minerals can be a fun hobby, in part because there are so many types to identify. There are many tests you can perform without specialized equipment to narrow down the number of possibilities, and on this page we provide you with a helpful overview of common minerals to compare with your results. You can even skip straight to the descriptions to see if a specific question you have is easily answered without having to take the test. For example, this article will teach you how to distinguish true gold from other glowing, yellow minerals (above the bright, colorful, striped bands you find in rocks) or help you identify a strange mineral that flakes off when rubbed.
Steps
Part 1 of 2: Perform tests
Step 1. Distinguish between minerals and rocks
A mineral is a combination of chemical elements that occurs in nature in a certain structure. While a single mineral can emerge in different shapes or colors due to geological processes or minute amounts of impurities, generally each example of that mineral will have certain characteristics that can be tested for. Rocks, on the other hand, can be formed from a combination of minerals and do not have a crystal structure. They are not always easy to tell apart, but if tests produce different results for one part of an object than another, the object is likely a rock.
You can also try to identify rocks, or at least identify which of the three types of rocks they belong to
Step 2. Understand mineral identification
There are thousands of minerals on Earth, but many of them are rare or only found deep underground. Sometimes two or three tests are all it takes to reduce the unidentified substance to a common and probable mineral listed in the next section. If the characteristics of the mineral don't fit any of those descriptions, try finding a mineral identification guide for your area. If you've done a lot of testing and can't identify a mineral out of two or more possibilities, look online for photographs of each possible mineral and specific tips for distinguishing those minerals.
It is best to include at least one test that involves an action, such as the hardness test or the grain test. Tests that only involve observing and describing the mineral may not be helpful on their own, as different people will describe the mineral in different ways
Step 3. Examine the shape and surface characteristics of the mineral
The general shape of each mineral crystal and the pattern of a group of crystals is called habit. There are many technical terms that geologists use to describe this, but a basic description is often sufficient. For example: is the mineral bulky or smooth? Is it a collection of rectangular crystals mixed with each other or thin, pointed crystals pointed outward?
Step 4. Observe the shine of the mineral or luster
Luster is the way a mineral reflects light and while it is not scientific proof, it is often helpful to include it in descriptions. Most minerals have either a glassy (or vitreous) or metallic luster. You can also describe a shine as greasy, pearly (an off-white sheen), earthy (opaque, like unglazed ceramic), or whatever description makes sense to you. Use multiple adjectives if necessary.
Step 5. Take a look at the color of the mineral
For most people, this is one of the easiest tests to perform, but it is not always helpful. Small traces of other substances in the mineral can cause it to change color, so a mineral can have many different colors. However, if the mineral is an unusual color, such as purple, it can help you narrow down the number of possibilities.
When describing minerals, avoid difficult-to-define colors such as "salmon" and "reddish brown." Stick to simple terms like "red," "black," and "green."
Step 6. Perform the vein test
This is a useful and easy test, as long as you have a piece of white, unglazed porcelain. The back of a kitchen or bathroom tile can work well; See if you can buy one from a DIY store. Once you have the porcelain, simply rub the mineral onto the tile and see what color "streak" it leaves. Often times this vein is a different color from the large chunk of ore.
- Glazing is what gives porcelain and other ceramic objects their glassy shine. An unglazed piece of porcelain does not reflect light.
- Keep in mind that some minerals do not streak, particularly the harder minerals (because they are harder than the porcelain they rub against).
Step 7. Test the hardness of the material
Geologists often use the Mohs hardness scale, named after its creator, to quickly estimate the hardness of a mineral. If you are successful with test 4 but not with 5, the hardness of the mineral is between 4 and 5, and you can stop testing. Try to leave a permanent scratch using these common materials (or minerals found in mineral hardness test kits), starting with the lowest numbers and moving up if the test is successful:
- 1: It can be scratched easily with the nail, it feels greasy and smooth (talcum powder).
- 2: It can be scratched easily with the nail (plaster).
- 3: It can be easily cut with a knife or nail, or scratched with a penny (calcite).
- 4: can be easily scratched with a knife (fluorite).
- 5: it can be scratched with a knife with difficulty, or scratched with a piece of glass (apatite).
- 6: It can be easily scratched with a steel file, scratches a piece of glass with difficulty (orthoclase).
- 7: scratch a steel file, easily scratch a piece of glass (quartz).
- 8: scratches quartz (topaz).
- 9: scratch almost everything, cut glass (corundum).
- 10: scratch or cut almost everything (diamond).
Step 8. Break up the mineral and watch it come apart
Because each specific mineral has a certain structure, it must be broken in a certain way. If the break results in one or more planar surfaces, this shows exfoliation. If there are no flat surfaces, just curved or uneven lumps, the broken ore has fracture.
- Exfoliation can be described in more detail by the number of flat surfaces a rupture creates (usually between one and four) and whether the surface is perfect (smooth) or imperfect (rough).
- The fracture comes in several types. Describe it as chipped (or fibrous), sharp and serrated (chopped), bowl-shaped (conchoid) or none of the above (irregular).
Step 9. Perform other tests if you still cannot identify the mineral
There are many other tests that geologists perform to identify a mineral. However, many of these are almost never used for common minerals, or they may involve specialized equipment or hazardous materials. Here are brief descriptions of some tests that you may be interested in running:
- If the mineral sticks to a magnet, it is most likely magnetite, the only common strongly magnetic mineral. If the attraction is weak, or the descriptions of the magnetite don't match the mineral, it could be pyrrhotite, franklinite, or ilmenite.
- Some minerals melt easily with a candle or a dimmer flame, while others will not melt even with a torch flame. Minerals that melt easily have a higher "fusibility" than minerals that are more difficult to melt.
- If the mineral has a noticeable odor, try describing it and search online for a mineral with that odor. Strong odor minerals are not common, although deep yellow mineral sulfur can react to produce the smell of rotten eggs.
Part 2 of 2: Identify Common Minerals
Step 1. Check the previous section if you don't understand a description
The descriptions below use various terms or numbers to describe the shape, hardness, appearance after breaking, or other attributes of the mineral. If you're not sure what they mean, see the section on testing above for an explanation.
Step 2. The most common crystalline minerals are quartz
Quartz is an extremely common mineral, and its sparkling or crystalline appearance draws the attention of many collectors. Quartz has a hardness of 7 on the Mohs scale and shows any kind of fracture when broken, never the flat surface of the exfoliation. Does not leave a noticeable streak on white porcelain. Has a glassy luster or luster.
- The milky quartz is translucent, the pink quartz it's pink and the amethyst it is purple.
Step 3. Hard, glassy minerals without crystals can be a different type of quartz called chert
All types of quartz are crystalline, but some varieties, called "cryptocrystalline," are made of tiny crystals that are not visible. If the mineral has a hardness of 7, fractures, and a glassy luster, it may be a type of quartz called chert. This is most commonly brown or gray.
Flint is a variety of chert, but it is categorized in different ways. For example, some people may refer to any black chert as flint, while others may only call it flint if it has a certain luster or was found among certain types of rock
Step 4. Striped banded minerals are generally a type of chalcedony
Chalcedony is formed from a mixture of quartz and another mineral, moganite. There are many beautiful varieties that usually form striped bands of different colors. These are two of the most common:
- Onyx is a type of chalcedony that tends to have parallel bands. It is often black or white, but it can have many colors.
- Agate has more curved or meandering bands and can come in a wide variety of colors. It can be formed from pure quartz, chalcedony, or similar minerals.
Step 5. See if the characteristics of your mineral match those of the feldspar
In addition to the many varieties of quartz, the feldspar it is the most common type of mineral found. It has a hardness of 6, leaves a white streak, and can have various colors or luster. It forms two flat peels when broken, with surfaces that are fairly smooth and almost at right angles to each other.
Step 6. If the mineral peels off when you rub it, it is probably mica
This mineral is easily identified because it peels off into thin, flexible sheets when scratched with your fingernail or even rubbed with your finger. The muscovite mica or white mica is pale brown or colorless, while the biotite mica o Black mica is dark brown or black with a grayish-brown stain.
Step 7. Learn the differences between gold and the gold of the poor
The pyrite, also known as poor man's gold, has a metallic yellow appearance, but various tests can distinguish it from real gold. It has a hardness of 6 or more, while true gold is much softer, with a hardness of between 2 and 3. It leaves a greenish black streak and can be crushed to a powder if enough pressure is applied.
- The Marcasite it is another common mineral similar to pyrite. Although pyrite crystals are cube-shaped, marcasite forms needles.
Step 8. The green and blue minerals are often malachite or azurite
Both of these minerals contain copper, among other minerals. Copper gives the malachite its deep green color, while making the azurite appear bright blue. These minerals often occur together, and both have a hardness between 3 and 4.
Step 9. Use a mineral guide or website to identify other types
A mineral guide specific to your area will cover other common types of minerals found in that region. If you are having difficulty identifying a mineral, some online resources, such as minerals.net, allow you to look up your test results and match them with possible minerals.