Minerals & Their Properties — Practice · Grade 9 Science

Chapter: Rocks, Landscapes & Water

What this practice covers

By the end of Minerals & Their Properties you should be able to:

10 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: mineral, luster, streak, hardness.

Problem 1

Which of these is NOT one of the five traits required for a substance to be classified as a mineral?
  1. Naturally occurring
  2. Made of living tissue
  3. A solid
  4. Definite chemical composition
Answer and explanation

Made of living tissue

Minerals must be inorganic — not created by living organisms; the other three are indeed required traits.

Problem 2

Which property is generally the LEAST reliable for identifying a mineral?
  1. Streak
  2. Color
  3. Hardness
  4. Luster
Answer and explanation

Color

Color is unreliable because trace impurities can cause the same mineral to appear in several different colors.

Problem 3

A mineral breaks apart along smooth, flat surfaces that follow its internal crystal structure. This property is called…
  1. fracture
  2. cleavage
  3. luster
  4. streak
Answer and explanation

cleavage

Breaking along smooth, flat planes that follow the crystal structure is cleavage; uneven, rough breakage is called fracture.

Problem 4

Diamond has a Mohs hardness of 10 and talc has a Mohs hardness of 1. How many whole steps higher is diamond's hardness than talc's?
Answer and explanation

9

10 − 1 = 9.

Problem 5

A student says two minerals must be different because one sample is purple and the other is white. Explain why color alone is not enough evidence, and describe a better test.
Answer and explanation

Many minerals occur in several colors because of trace impurities — for example, quartz can be purple (amethyst), pink (rose quartz), or clear — so two different-colored samples could still be the same mineral. A better test is to compare streak (the color of the powdered mineral) or hardness, which don't change with impurities the way color does.

Problem 6

Sample A scratches calcite (3) but is scratched by fluorite (4). What does this support? Explain the reasoning in your own words.
Answer and explanation

Its Mohs hardness lies between 3 and 4 under this test; other properties are needed for identification.

Scratch resistance exceeds calcite's but is below fluorite's.

Use the ranking as a bracket, not as an exact numerical average.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

Two minerals share a color. Give two stronger comparison tests. Show the reasoning, not just the conclusion.
Hints

Hardness is scratch resistance, not how easily a sample breaks.

Answer and explanation

Streak, hardness, cleavage, density or other characteristic properties can distinguish them; choose two and describe the tests.

Problem 8

Why should a weathered surface be avoided in a streak or hardness comparison?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Weathering products can have different properties from the fresh mineral being identified.

Problem 9

A broken face is different from a crystal’s growth faceA broken face is different from a crystal’s growth faceRepeated planar break surfacesIrregular break surfaceCleavage follows structural planes.Fracture has other break geometry.
Original schematic specimen shapes illustrate planar and irregular break geometry. No named mineral is identified by these cartoons. They separate observations of breakage from growth form and do not replace hands-on or photographed specimen evidence.
Interpret the supplied visual model. What observation would distinguish a crystal growth face from evidence of cleavage?
Answer and explanation

Record whether the surface formed during growth or breakage, and look for repeated characteristic planes/angles across breaks. A flat appearance alone is insufficient.

Compare repeated planes on the left with irregular geometry on the right. These are schematic specimen surfaces rather than exact identification photographs.

Record whether the surface formed during growth or breakage, and look for repeated characteristic planes/angles across breaks. A flat appearance alone is insufficient.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 10

A specimen has mass 54 g and displaces water from 20 to 38 mL when fully immersed without bubbles. Find its density and explain what additional evidence is needed to identify its mineral.
Answer and explanation

Volume is 18 mL = 18 cm³, so density is 54/18 = 3 g/cm³. Use hardness, streak, cleavage and other characteristic observations; density alone may match several candidates.

Find displaced volume: 38−20 = 18 cm³.

Calculate density: 54/18 = 3 g/cm³.

Compare several tests and uncertainty rather than naming a mineral from one value.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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