Teachers TryScience

Ask Students:

• What do you already know about identifying minerals?
• How would you describe the rocks, gems or minerals you have already seen?

The Big Idea

• Gather children into one large group.
• Hold to rocks up for the children to see. Pass some samples around.
• Encourage Students in providing descriptions of the rocks and minerals, describing what they “see” and “feel”.
• Ask the children to please tell you all the ways that they know of to identify, sort, or organize these two rocks.
• Write the students’ descriptions on the white board. For example, rough, smooth and bumpy all describe “Texture”. Other groups to be discussed: Hardness, Color and Luster.
• Next, ask the children to tell you how you can tell if one rock is harder than the other. Listen to the children’s ideas, and test any of their hypotheses. A few of these tests might include chipping the rock with some sort of tool, banging the rocks together, or tapping the rocks to hear what sound they may make.
• Explain that scientists to use the different properties of rocks for identification and classification. Properties include: color, buoyancy, and hardness.

Rock Properties:

Teach students the term “properties” – distinctive characteristics or qualities belonging to something. Examples:

• Properties of a pine tree are cones and needles.
• Properties of birds are feathers and wings.

Activity 1: Rock and Mineral ID (Contribution by Janis Tipton King)

Materials:

• Hardness Test Kit- use the Geol. Field kit

• Streak plate or tile use the Geol. Field kit

• acetic (or other) acid and dropper (in kit)

• Paper towel to work on!!!

• Hand lens (in kit) or dissecting scope

• Rock and Mineral book(s) shared by the class

• 1 Mineral or rock sample

  Procedures:

• Group students into fours and provide each group with 10 rocks. Ask each group to come up with as many ways as they can think of to test the hardness of the rocks, and to put them in order from weakest to strongest. Ask them to keep their rocks in this order when they are finished so that the rest of the class can observe what everyone has done.

• Look at your sample over, use a hand lens and examine it too.

• Feel its texture.

• Use the geo-speak words to help you and write a complete description of your mystery sample:

• Magnetic? Or not?

• Does it look as if the sample broke along set lines or in a pattern?

  Tell Students: This is called a cleavage plane. If so use the book to help you describe the pattern.

• Use the hardness test kit and following the directions below determine its hardness. Write down the number down.

  Explain: You are going to use a series of things to try and put a very small scratch on your sample. Each thing in order increases in hardness. Start with the lowest number which is the softest item. If that thing scratches your sample your hardness is that. This rarely happens. So try the next thing. Does it scratch? If not try the next harder thing and so on but only until it makes a scratch. Then STOP. The hardness # is 1 less than the thing that scratched it. Example: My mystery mineral could not be scratched by my fingernail, it couldn’t be scratched by a penny but it did get scratched by the glass (5.5) so my mineral has a hardness of about 4-5.

  If it were scratched by the penny (3.5), but not my fingernail (2) then it’s hardness would be about a 3.So one less than the thing that scratched it as you work up the scale. Make sense?

• Test your sample for a possible colored streak. This is as easy as it sounds. Certain minerals may leave a colored streak (mark) on the back of an unglazed tile. All you do it rub it as if you were trying to write with it on the tile’s unglazed side. A small mark will do. Try it on a white tile and then also on a black one (in case it leaves a white streak) It left no mark _____It left a ____________colored mark.

• To test for carbonates in the sample:

• Place a few drops of vinegar/acetic acid on the sample. Look carefully for tiny bubbles. Give it a minute or so and look again. Bubbles are an indication your sample contains carbonates. Rinse your sample (unless you think it could be halite!) off in water and pat dry.

• You may need to plop your sample into a small jar of acid to tell for sure. The bubbles are more obvious HOWEVER you stand to dissolve your mineral!

• Yes, I had bubbles and therefore carbonates _____

• Nope! ____

• Does it glow under UV light? ____Yes!____No

• Look carefully to see if your sample has any crystals.

• If so what is their shape?

• How many sides do they have? Are they pointed?

• And are the crystals all the same shape do you think?

• No crystals

• Now using your description, cleavage plane (if any), color streak (if any), presence of carbonates (if any) , crystal shape (if any) and hardness # to look your sample up ina book of rocks and minerals.

  Read the description and look at the photos. Rely on the description much more than the photo. Do you think you have this? If not, then try a few others that have similar features. Now what do you think you have?

• < >

  The box marked Hardness Set

• The box marked Cleavage Set

• The box marked Streak Set

  Procedures:

• Tell Students: Now try a different sample. And this time you can use the mineral hardness box set and the cleavage plain mineral set instead of the field kit.

• New Added Materials: Do not mix up the minerals!!!! Every sample has a unique place in its box and belongs only on that box. So open one at a time. Take out only one mineral at a time to use and put it right back.

• A new mystery rock or mineral- ask your teacher

• The box marked Hardness Set

• The box marked Cleavage Set

• The box marked Streak Set

• Start by a description of the texture and luster like above:

• Then try the magnet: ______Magnetic!____________No

• Test for carbonates with the acid. _________Bubbles!________No

• How about trying a UV light? Place your mineral under the light and see if it fluoresces i.e. glows in the dark with UV light. Mine did! ____No____

• Now get the Hardness box set. This has “the mineral for each hardness”. Start with your fingernail. If it scratches then go to the box and try the softest mineral with a hardness on 1. Be careful- a 1 is super soft so be very careful to as you scratch your sample. Next try #2 if #1 did not scratch. Then try #3

• If your fingernail did not scratch your mystery mineral, then go to the box and start with #3 and work your way up. You may need to use a magnifying lens to see a scratch. Remember your hardness is one less than the thing that scratched it. My hardness is ________________ scratched by ________________________________!

• We have examples of different cleavage planes. Open the Cleavage box and try and match your sample with a break direction or cleavage pattern in the boxed examples. My cleavage best matches _____________________ which is an example of _____________________cleavage.

• OR mine is probably a fracture like ___________

• We have boxed streak color examples. So use the white tile and try and make a small mark with your mystery mineral. Did it leave a color mark? Write it down if so- mine left a __________________colored streak.

• If not, try it on the black tile. Did it leave a streak? If so I bet it was white. Mine left a _______________________streak.

• Now. . .we have a box of nifty minerals that might or might not match up to yours. Use the Streak Box and compare the mineral that has the same streak color to yours. Any match? _______Yes! So I might have a ____________________________.No!_______

• Now you’ve collected about all the information you can on your sample. Use your info. and the books and charts to try and Identify your mystery mineral. Mine is: _____________________________
• If there is time, get one more mystery mineral or rock and repeat the process.

Activity 3: Fossil (Contribution by Janis Tipon King)

Materials:

• Phony Fossil

• Dissection Probe

Work on the diaper pad

Procedures:

• Explain to Students: Some people can go their entire lives and never see a fossil in the wild. You live in an area that has fossils all over so you’d have to be pretty unobservant to not find one! Today you are going to try and remove a phony fossil from its matrix, just like you would do if it were real.

• We’ll probably uncover uplifted seabed in our field work. That means marine critters and especially their shells. This is more often than not from the Miocene (26 million years ago – 6mybp) a part of the Briones Formation made of sandstone, siltstone, pebble conglomerate and the interesting bit- marine shell hash! This was the floor of the Pacific Ocean 12 million years ago. An accumulation of shells form things like clams, oysters and anything else with a shell of calcium, carbonate settles and becomes a fossil. Most are preserved without change- that is the minerals have not been replaced, it is not just a print, it is not a carbon film and it didn’t leave a hole and wasn’t replaced with minerals (those are the other ways fossils form).

• What to do- very carefully as if you were trying to preserve a million dollar fossil find, scrape away at the matrix until you uncover a bit of your ”fossil”.

• Keep at it until you have it clean and free.

• So what- so this is how you free a fossil from its rock or uncover more fully a fossil for study. Great practice! Yes, you can keep it.