Mississauga Geode Earthcache EarthCache

It really is amazing what you can find within the quiet recesses of our own community.^* We marvel at the feats of an oyster to create beautiful pearls, but what of the natural geological processes that give us little treasures as well. Geodes are the beautiful presents that tumble and turn and grow within existing rock to form little pockets of crystalline beauty.

Logging Requirements (Please email me the answers to these tasks and keep the details out of your log.)

1. Take a look at the entire stretch of geodes and measure the largest one you found and the smallest and send me the sizes. What could this range tell us about their formation?
2. Take a look at the colours of the crystals inside the geodes, are they all the same? If they are not, describe the variations and explain why you think that might happen (in terms of geological process).

Optional Tasks:

3. Measure the size and amount of geodes in one rock and calculate the ratio (in surface area) of geodes to host rock by taking some measurements of it as well. Why do you think that ratio exists? What could have made that amount increase/decrease?
4. Take a picture of the coolest geode you could find and share it with us. This is not required to log the EC, it is totally optional, but feel free to do so.

When you reach this wall of geodes you will be amazed at how beautiful they can be and yet so unique from one to the next. I have always been amazed at how the geological processes of our planet are able to manifest in such wacky ways.

Geodes are rock formations that occur within other types of rock. For the most part they appear in sedimentary or volcanic rock, but wherever they are they contain a beautiful surprise.¹ They may appear like a small roundish (or bumpy) rock. They might even appear ugly, but the weight can be the key to identifying them. They are far lighter than rocks of the same size.

Time and energy are an amazing cocktail for geological formations and with geodes the proof is evident. Thousands of years ago while the surrounding rock was undergoing changes, small pockets of gas, moisture and minerals were trapped inside a host rock formation. The outer layer hardened and allowed dissolved silicates or carbonates to reach the inner surface. As time continued on and mineral rich groundwater is able to "fertilize" these pockets, crystals grow and remain there until the host rock is removed to leave these hard little "pearls" of wonder.²

The resulting crystals (usually quartz or calcite) are amazingly unique and at times can grow with such enthusiasm that they can fill the entire space. These are no longer referred to as geodes, they are nodules. With the concentration of colours and shapes varying from geode to geode you can spend hours analysing and comparing all the different types. You will see at least four different examples at GZ and all along this group of rocks. Keep track of the variations for the logging requirements. As we walk each day we can see evidence of our beautiful planet hard at work, have fun turning this walk in the park into an introduction to Geodes.

References

1. Geode on Wikipedia

2. Thunder Eggs & Geodes at the Australian Museum

* Special thanks to dezerter for showing me this location.