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As a geologist, you need to practice describing rocks in detail. It's not enough just to say "it's a rock". You need to be very specific and mention each of the properties that make one rock different from another.

Find a particularly interesting rock on your schoolyard. It can be either natural or man-made. Describe the rock in detail. If you aren't familiar with rocks already, refer to this web page. Here is a table that you can use to help guide you to describing rocks clearly. You'll describe the following properties:


Where did you find this rock? You may not remember in a few days, so write it down so that you can come back. Also, other people will be able to come see the rock you described.

  • Describe the colors as clearly as you can in words. For example, "dark brown" is different than "light brown" or "reddish brown."
  • Are any of the grains shiny or do they sparkle? Mention that!
  • If there is more than one color, describe each color. Also, mention if one color is the most common color. You can even quantify this using percentages: "50% white grains, 30% pinkish-grey grains, 20% shiny brownish-black grains."
Grain Size
  • It's not enough to just say that the grains are "big" or "small" because what you define as big might be small to someone else. As a scientist, you should measure the grains! Use a ruler to measure the grains. Don't worry, you don't need to measure them all!
  • Try to find one of the smallest grains (it shouldn't be the smallest in the entire rock, but one of the smallest) and measure its size. That is the minimum grain size. Then, measure one of the largest grains and record its length as the maximum grain size.
  • Sometimes grains are long and narrow. For those, write out "2 cm long by 0.5 cm wide."
  • If the grains are really tiny, you can write "grains too small to measure."
  • If the rock looks like one solid mass and you can't see individual grains, write, "grains too small to see."
  • Based on your measurements, are most of the grains about the same size?
Grain Shape

Look at the grain shape. Are the grains sharp and angular? Or are they rounded? Or are they somewhere in between? Circle the words that best describe the rock you are looking at.


Is the rock hard and solid, or is it a bit crumbly?

Other Comments

This is space for you to write anything else interesting about the rock.

All the same color?
Grain Size
Minimum grain size___ cm
Maximum grain size___ cm
All the same size?
SortingWell Sorted ... Medium Sorted ... Poorly Sorted
Grain shapesRounded ... Medium Rounded ... Medium Angular ... Angular
Other Comments

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