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Mineral Identification Guide Cheat Sheet
A printable reference covering mineral properties, hardness, streak, luster, cleavage, fracture, and density for grades 5-11.
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Mineral identification is the process of observing and testing a mineral to match it with known mineral properties. This cheat sheet helps students use a clear sequence: observe, test, and compare. It is useful because many minerals look similar, so color alone is not enough for reliable identification. Students need repeatable tests such as hardness, streak, luster, cleavage, fracture, and density. The most important idea is that each mineral has a specific combination of physical properties. Hardness compares how easily a mineral is scratched, while streak shows the color of its powder. Luster describes how the surface reflects light, and cleavage or fracture describes how the mineral breaks. Density can be calculated with density = mass / volume and used as another clue for identification.
Key Facts
- A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystal structure.
- Use the identification sequence observe → test → compare to avoid relying on one property alone.
- Hardness is measured by scratch resistance on the Mohs scale from 1 for talc to 10 for diamond.
- Streak is the color of a mineral's powder and is usually found by rubbing the mineral on an unglazed porcelain streak plate.
- Luster describes how a mineral reflects light, with common types including metallic, glassy, pearly, silky, dull, and earthy.
- Cleavage means a mineral breaks along flat, repeating planes, while fracture means it breaks unevenly or in curved surfaces.
- Density is calculated with density = mass / volume, using units such as g/cm3.
- Color can help describe a mineral, but it is often unreliable because impurities can change a mineral's appearance.
Vocabulary
- Mineral
- A mineral is a naturally occurring, inorganic solid with a definite chemical composition and an orderly crystal structure.
- Hardness
- Hardness is a mineral's resistance to being scratched, measured using the Mohs hardness scale.
- Streak
- Streak is the color of the powder a mineral leaves when rubbed across an unglazed streak plate.
- Luster
- Luster is the way a mineral's surface reflects light, such as metallic, glassy, dull, or pearly.
- Cleavage
- Cleavage is the tendency of a mineral to break along flat, smooth planes caused by its crystal structure.
- Density
- Density is the amount of mass in a given volume and is calculated with density = mass / volume.
Common Mistakes to Avoid
- Using color as the main identification test is wrong because impurities and weathering can make the same mineral appear in many colors.
- Confusing streak with surface color is wrong because streak is the powdered color, which can be different from the visible outside color.
- Calling every flat surface cleavage is wrong because a broken surface may be a random fracture instead of a repeated flat break pattern.
- Scratching the mineral with too much force is wrong because pressure can leave marks or damage the sample without proving true hardness.
- Forgetting units in density is wrong because density must compare mass and volume, such as g/cm3, to be useful for identification.
Practice Questions
- 1 A mineral has a mass of 48 g and a volume of 16 cm3. What is its density?
- 2 A mineral scratches a copper penny but is scratched by a steel nail. What hardness range does this suggest if a penny is about 3 and a steel nail is about 5.5 on the Mohs scale?
- 3 A sample leaves a black streak, has metallic luster, and breaks unevenly. List the three properties used in this description.
- 4 Why should a student use several mineral tests instead of identifying a mineral by color only?