There's Quartz in them thar hills EarthCache
There's Quartz in them thar hills
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This Earthcache requires you to visit 2 waypoints along the Chattooga River Trail. Coordinates are averaged but there is lots of tree cover so when you get close start to look for what is described below.
In geology, a vein is a distinct sheet like body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation.
Veins are classically thought of as being the result of growth of crystals on the walls of planar fractures in rocks, with the crystal growth occurring normal to the walls of the cavity, and the crystal protruding into open space. This certainly is the method for the formation of some veins. However, it is rare in geology for significant open space to remain open in large volumes of rock, especially several kilometers below the surface. Thus, there are two mains considered likely for the formation of veins: open-space filling and crack-seal growth..
Open Space Filling - Open space filling is the hallmark of epithermal vein systems, such as a stockwork, in greisens or in certain skarn environments. For open space filling to take effect, the confining pressure is generally considered to be below 0.5 GPa. (measure of force per unit area) Veins formed in this way may exhibit a colloform, agate-like habit, of sequential selvedges of minerals which radiate out from nucleation points on the vein walls and appear to fill up the available open space.
Crack-seal veins - When the confining pressure is too great vein formation occurs via crack-seal mechanisms. Crack-seal veins are thought to form quite quickly during deformation by precipitation of minerals within incipient fractures. This happens swiftly by geologic standards, because pressures and deformation mean that large open spaces cannot be maintained; generally the space is in the order of millimeters or micrometers. Veins grow in thickness by reopening of the vein fracture and progressive deposition of minerals on the growth surface.
At the 1st waypoint (actual Earthcache coordinates) you are looking for a slab of rock that is approximately 4 feet in length and 2 feet in width. When you find this rock answer the question below:
1. What portion (%) of the rock do you think is made of Quartz?
2. Which mechanism is most likely to have formed the vein at waypoint #1?
When you arrive at the 2nd waypoint you will be standing on a large rock in the middle of a small stream that crosses the trail. (Be careful as this rock is very slippery!) You will see a Quartz vein running through the rock. Find it and answer the questions below:
3. On the far right end of the vein (right end if the river is on your left) tell what you think the width, at its largest portion, of the vein is?
4. Tell how long, in length, you think the vein is?
5. Which mechanism is most likely to have formed the vein at waypoint #2?
Email your answers to my profile and please do not put any answers in your log.
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