At GZ, you will find a series of large rocks that are used as a landscaping feature for the playground. These rocks are no ordinary rocks - they contain a collection of vugs and geodes - crystaline structures formed in air pockets of the rocks. "Geodes are the beautiful presents that tumble and turn and grow within existing rock to form little pockets of crystalline beauty."
Vugs (also spelled: vugh, or vugg)
A vug is a small to medium-sized cavity inside rock. It may be formed through a variety of processes, but most commonly are cracks and fissures opened by movement (either tectonic or seismic activity), which are partially filled by quartz, calcite, and other minerals. Open spaces within ancient rocks or lava collapse breccias are another important source of vugs. These types of vugs are typically caused by minerals or sediment located within the pockets, which crystalize under intense pressure.
Vugs may also form when crystals or fossils inside a rock are removed through erosion or dissolution processes such as decaying organic matter, leaving behind holes with organic or mineral compounds. The inner surfaces of such vugs are often coated with a crystal druse (a coating of fine crystals on a rock fracture surface, vein or within a vug).
Fine crystals are often found in vugs where the open space allows for the crystals to form. The term vug is not applied to veins and fissures that have become completely filled, but may be applied to any small cavities that are not completely filled. Once they are completely filled, they are called NODULES.
Geodes
Geodes are a common vug-formed rock, although that term is usually reserved for more rounded crystal-lined cavities in sedimentary rocks and ancient lavas. Geodes are rock formations that occur within other types of rock, typically crystaline in nature. 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.The resulting crystals (usually quartz or calcite) are unique and will vary in colour depending on the mineral composition, but the most common are white, light gray or dark grey.
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.
Details About this Earthcache
Parking is available roadside, but please do be cautious of no stopping signs and fire hydrants in the area. This can be a VERY busy area in the summer, especially on the weekends, as it is close to a children's playground. This park area is available from 8am until 10pm, 7 days per week. However, due to the close proximity to homes in the area, and due to the visual nature of earthcaches, I would ask that you please limit your visit to daylight hours.
This earthcache will not be available when there is excessive snow on the ground. Please be respectful and come back when you are able to fully experience the fossils.
As with all of my ECs, I am not looking for PhD thesis level responses, but I am hoping that you take some time to enjoy the area and learn something new. Please include a list of all cachers with your answer, if answering for more than one caching name.
Logging Requirements
In order to claim a find, please send the answers to the following questions to the CO using the Message feature at the top of this page.
1). Would you classify these as vugs or geodes? Why do you think that it is one and not the other?
2) MANDATORY - take a picture of your favourite crystal growth, and attach it to your log. In your message to the CO, indicate the approximate length, width and depth of the crystals in this structure.
3) Take a close look at the crystal growth in the cavities at GZ. Describe the colour, shape and texture. Do the completely fill the cavities, or are they more of a lining?
4) Based on the information in the cache page as well as what you see at GZ, how do you think that these crystals would have formed?
5) Do you think that the mineral composition of the crystals is all fairly similar, or does it vary between crystaline structures?
6) Approximately how many crystal structures are located within a 1 foot by 1 foot section of rock?
7) Are there any sections where you think see signs of weathering on the crystals? Does it look like any of these crystals could be removed, or do you think they are solid within the stone?
Other photos are welcome of yourself or your group in the area. Please feel free to log as found as soon as you send your answers and I will contact you if you have any questions. Logs without answers sent may be deleted if answers are not received within 5 days of logging.
This cache was placed by a proud Platinum Earthcache Master.