You will be able to identify minerals by their colors and streaks, and be able to tell a sample of real gold from the fake look-alike called pyrite.
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Materials
- 1 handheld magnifying lens
- Unglazed porcelain tile
- Rock samples (the ones in the video are: graphite, pyrite, talc, iron, and jasper)
Download worksheet and exercises
Every mineral has a set of unique characteristics that geologists use to test and identify them. Some of those tests include looking at the color of the surface, seeing if the mineral is attracted to a magnet, dripping weak acids on the rock to see if they chemically react, exposing them to different wavelengths of light to see how they respond, scratching the rocks with different kinds of materials to see which is harder, and many more. There are more than 2,000 different types of minerals and each is unique. Some are very hard like diamonds, others come in every color of the rainbow, like quartz and calcite, and others are very brittle like sulfur.
The color test is as simple as it sounds: Geologists look at the color and record it along with the identification number they’ve assigned to their mineral or rock. They also note if the color comes off in their hands (like hematite). This works well for minerals that are all one color, but it’s tricky for multi-colored minerals. For example, azurite is always blue no matter where you look. But quartz can be colorless, purple, rose, smoky, milky, and citrine (yellow).
Also, some minerals look different on the surface, but are really the same chemical composition. For example, calcite comes in many different colors, so surface color isn’t always the best way to tell which mineral is which. So geologists also use a “streak test”.
For a streak test, a mineral is used like a pencil and scratched across the surface of a ceramic tile (called a streak plate). The mineral makes a color that is unique for that mineral. For example, pink calcite and white calcite both leave the same color streak, as does hematite that comes in metallic silvery gray color and also deep red. This works because when the mineral, when scratched, is ground into a powder. All varieties of a given mineral have the same color streak, even if their surface colors vary. For example, hematite exists in two very different colors when dug up, but both varieties will leave a red streak. Pyrite, which looks a lot like real gold, leaves a black streak, while gold will leave a golden streak.
The tile is rough, hard, and white so it shows colors well. However, some minerals are harder than the mineral plate, like quartz and topaz, and you’ll just get a scratch on the plate, not a streak.
- Number your rock samples by placing them on your data table.
- Using your data table, record the color of each sample.
- Now use your streak plate. Take a rock and draw a short line across your streak plate (unglazed porcelain tile).
- Record the color of the streak in your data table. Are there any surprises?
Exercises
- What does it mean if there’s no streak left?
- Give an example of a kind of rock that leaves a streak a different color than its surface color.
- What is a mineral that appears in two different colors, yet leaves the same color streak?
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You can go in any order you like! The first test geologists usually do is look at the rock and record the color of it. Is that the other reference you are referring to? There isn’t a video for looking at the color, but there is information describing how to do this in the text area right under the video.
There’s also an experiment that walks you through how to test different rocks using all the different tests we cover, which you can find here:https://www.sciencelearningspace2.com/2013/09/geology-field-trip/
At the end of the video, we start to talk about hardness, which is the next video in the series:
https://www.sciencelearningspace2.com/2013/09/mohs-hardness/
Let me know if you need anything else!
In what order should these lessons be taught? We were going to start with Color Streak but you reference another video during the Color Streak video.
Sure! The shopping list for Unit 20 is here:
https://www.sciencelearningspace2.com/2013/09/shopping-list-for-unit-20/
I have attempted to find the shopping list that goes along with Unit 20 (I read another comment first) and I cannot find it. Can you please link the shopping list to find the rock samples for this lesson as well as other lessons for Earth Science Grade 2? Thanks
I’ll have my team connect with you right away!
We would really like to do the geology unit. Can we get access to that?
Thank you.
Look in the shopping list for this unit – use the link on the right when you’re in the main level for unit 20. You’ll find links to online ordering stores.
Where can I obtain rock samples for this experiment?
You’ll want to watch the electricity teleclass – that’s something we go over in detail. 🙂
https://www.sciencelearningspace2.com/2014/10/science-teleclass-electricity/
Hi! My sister wanted to know what happens when water and electricity touch. Thanks!
-Olivia
That was cool!
-Olivia
I’ll have my team connect with you right away!
Can we get access to this unit?
I’ll have my team connect with you right away!
can I have aceses to this uint
My team will connect with you right away!
We are doing the trial and my daughter really wants to do the Earth Science section. Can we have access to that?
I’ll have my team connect with you right away!
Hello Aurora.
I’m using your program in combination with a science book and we are currently on the rocks and minerals unit. May I please have access to that unit?
Thank you so much.
Tabitha
Sure thing Nora! I’ll have my team connect with you right away!
I am preparing my lesson outline for next year. Could I please have access to the Earth Science and Human Anatomy/Physiology sections? I must complete by Thursday, Jan. 31 and just found your site and joined with the monthly subscriptions.
Thank you.
Nora
I am really excited about having this organized by grade level. I am homeschooling my ten kids and it was pretty difficult to have them try to do the same experiments at the same time. Often the concepts were too simplified or too complex for everyone. We are doing a science focus in Jan. I hope everything is up and running by then!
I’ll have my team contact you right away to get you set up with what you need in terms of access. Since the grade level organization is new, we’re still working out the kinks in getting folks access to the parts they need.
Not every experiment has a worksheet download with it, but there are some that have not yet been uploaded (we’re still getting them posted to the website, and there’s a lot of them to do!) Most of the experiments will have a worksheet when we’re done publishing them to the website, but you may still find a few that don’t. 🙂
Thanks for your patience.
I just signed up for this website. I can access the topics but not the experiments at my son’s grade level. He is in 4th grade and for example I can access the energy topic but when I try to access experiments for 4th grade energy studies I have no access. How long do I have to wait until I get access to everything? Also I noticed there doesn’t seem to be a download lesson or student experiment worksheet with the topics by grade level.