9.32 Mineral Identification

When we think of minerals, we tend to think of expensive ones, like gold and diamonds, but minerals are all around us. In this lesson you’ll learn about some of the different ways to identify minerals around you

What Is a Mineral?

While you’re out on the playground you find a pretty rock. You notice different colors, textures, and stripes. What are those different materials? Those are minerals. Minerals are natural, non-living substances found in rocks. Rocks are like chocolate chip cookies, and minerals are like the ingredients in the cookies. Just like you need flour and sugar to make cookies, you also need minerals to make rocks. We identify minerals by their properties, or characteristics. Color, luster, streak, and hardness are the properties that you will learn more about.

1. Main points:

Minerals are natural, non-living substances found in rocks, and they have specific properties like color, luster, streak, and hardness.

2. Questions:

– Content Analysis: What are minerals and where can they be found?
– Linguistic Analysis: What analogy is used to explain the relationship between rocks and minerals?
– Thematic Analysis: What properties are used to identify minerals?

3. Further Discussion:

How do you think the different properties of minerals affect their appearance and usage?

4. Answers:

– Content Analysis: "Minerals are natural, non-living substances found in rocks."
– Linguistic Analysis: "Rocks are like chocolate chip cookies, and minerals are like the ingredients in the cookies."
– Thematic Analysis: "Color, luster, streak, and hardness are the properties that you will learn more about."

I hope this analysis helps to clarify the text for young learners! Is there anything else you’d like to explore?

Color

Minerals can be any color in the rainbow. Some minerals, like amethyst, are always the same color (purple). Other minerals, like quartz, can be many different colors. Color is one way to identify a mineral, but because some minerals can be various colors there needs to be other properties that we observe to accurately identify them. Using all of the properties together will give us the best picture.

1. Main points:

Minerals can have various colors, but color alone is not sufficient to identify them; other properties are also important.

2. Questions:

– Content Analysis: What examples of minerals with specific colors are given?
– Linguistic Analysis: How is color described as a way to identify minerals?
– Socio-cultural Analysis: Why might the color of minerals be important or interesting to people?

3. Further Discussion:

Do you think the color of a mineral could influence its value or popularity? Why or why not?

4. Answers:

– Content Analysis: "Some minerals, like amethyst, are always the same color (purple). Other minerals, like quartz, can be many different colors."
– Linguistic Analysis: "Color is one way to identify a mineral, but because some minerals can be various colors there needs to be other properties that we observe to accurately identify them."
– Socio-cultural Analysis: The text doesn’t provide information on why the color of minerals might be important or interesting to people.

Luster

Luster is the way light reflects off a mineral. When you hold it up to the light it can look metallic, dull, shiny, glassy, or pearly. A mineral that has a metallic luster looks like it is made from metal.

Calcite has a glassy luster.
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Some minerals have more than one luster. If you can determine its luster, you are another step closer to identifying your mineral.

1. Main points:

Luster describes how light reflects off a mineral, and it can appear in various ways like metallic, dull, shiny, glassy, or pearly.

2. Questions:

– Content Analysis: What types of luster can a mineral have?
– Linguistic Analysis: How does the text describe the appearance of a mineral with a metallic luster?
– Thematic Analysis: What is the main focus when discussing luster?

3. Further Discussion:

How do you think the luster of a mineral could affect what it’s used for?

4. Answers:

– Content Analysis: "When you hold it up to the light it can look metallic, dull, shiny, glassy, or pearly."
– Linguistic Analysis: "A mineral that has a metallic luster looks like it is made from metal."
– Thematic Analysis: "Luster is the way light reflects off a mineral."

I hope these sections help clarify the topics of color and luster in minerals for young learners. Is there anything else you’d like to dive into?

Streak

If you take the rough edge of a mineral and scrape it across a tile it leaves behind a colored powder. That powder is the mineral’s streak. The color can be the same as the color of the mineral, but often times it is a different color or shade. Even when a mineral like quartz has different colors, it will still have the same color streak every time.

Pyrite has a streak that is blackish-green and rhodochrosite has a white streak.
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1. Main points:

Streak is the colored powder left behind when a mineral is scraped across a tile, and it can be different from the mineral’s own color.

2. Questions:

– Content Analysis: What is a mineral’s streak?
– Thematic Analysis: How does the streak of a mineral relate to its color?
– Linguistic Analysis: What action is required to discover a mineral’s streak?

3. Further Discussion:

How might the streak test help you to identify minerals more accurately than just by looking at them?

4. Answers:

– Content Analysis: "That powder is the mineral’s streak."
– Thematic Analysis: "The color can be the same as the color of the mineral, but often times it is a different color or shade."
– Linguistic Analysis: "If you take the rough edge of a mineral and scrape it across a tile it leaves behind a colored powder."

Hardness

One of the most important properties of minerals is its hardness. Hardness is a mineral’s tendency to scratch or be scratched by other minerals and materials. If a mineral can be easily scratched it is soft. A mineral that can scratch other things is hard. A scientist named Friedrich Mohs developed a scale to show the hardness of minerals. Every mineral is given a number 1-10. Talc, one of the softest minerals, has a rating of 1, and diamonds are a 10, because they are the hardest. You can use common items such as copper pennies, nails, steel files, and pieces of glass to scratch and test the hardness of minerals.

Pyrite: color – gold or brassy yellow, luster – metallic, streak – greenish-black, hardness – 6-6.5
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Looking at the above example of pyrite, you can see how color, luster, streak, and hardness can give important information about the mineral.

1. Main points:

Hardness is a property that describes a mineral’s ability to scratch or be scratched, and it’s measured on a scale from 1-10 developed by Friedrich Mohs.

2. Questions:

– Content Analysis: What does hardness indicate about a mineral?
– Thematic Analysis: How is hardness measured?
– Linguistic Analysis: Who developed the scale for measuring hardness and what are the scale’s extremes?

3. Further Discussion:

Why do you think knowing the hardness of a mineral might be important for its uses?

4. Answers:

– Content Analysis: "Hardness is a mineral’s tendency to scratch or be scratched by other minerals and materials."
– Thematic Analysis: "Every mineral is given a number 1-10."
– Linguistic Analysis: "A scientist named Friedrich Mohs developed a scale to show the hardness of minerals. Talc, one of the softest minerals, has a rating of 1, and diamonds are a 10, because they are the hardest."

I hope this helps young learners understand the properties of minerals better! Would you like to explore anything else?

Lesson Summary

Now it’s your turn to use your observational skills and be a scientist. Next time you pick up a mineral check out its color, luster, streak, and hardness. You can take all you have learned about the properties of a mineral and use them to help identify the ones all around you.