Welcome to Mississauaga Geodes! Please read logging requirements as set out below in order to log a find. Please send me an email with the required information, and do not post any answers in your log. Pictures are always encouraged, however, be sure that they do not give away any of the answers!
This earthcache brings you to a number of limestone blocks that line the Alberto Cataudella Memorial Trail. Dolostone is a sedimentary rock composed mostly of the minerals calcium, magnesium, carbon, and oxygen. Dolostone is formed from limestone via a process known as diagenesis, when magnesium in pore water is substituted for some of the calcium in the original limestone. As the magnesium takes up less physical space than calcium in the rock, void spaces form. These are small cavities within the rock and give dolostone its characteristic appearance.
What are Geodes?
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. 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.
How are Geodes Formed?
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.
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.
Quartz - Quartz crystals in Geodes form as a lattice with pyramid tips resembling hexagonal spikes that are attached to one another at the base. Pure Quartz is colourless and transparent but can also come in many colours like citrine, rose, amethyst, smoky, milky, and others and is dependant upon trace elements present.
Calcite - Calcite crystals in Geodes form as small individual triangular prism shapes resembling small "teeth". Calcite is a common constituent of sedimentary rocks, limestone in particular. Calcite is transparent to opaque and may show phosphorescence or fluorescence.
In order to log this earthcache, please email me the answers to the following questions:
1. What type of rock are these geodes formed in? Igneous or Sedimentary?
2. Explain how the Geodes were likely formed in these rocks?
3. What mineral are the crystals within these Geodes? Get a close look, look at the size and shape of the crystals.
4. MANDATORY - Take a photo of you or a personal item with the limestone blocks and post it with your online log. If you do not complete this part, your log will be deleted.
Congratulations to Mississauga Misfits on the FTF!