Nesting atop Lookout Mountain is a pretty, progressive hilltop community. Compared to surrounding areas, the TOWN of Sand Rock is relatively young, becoming incorporated in 1988. The Sand Rock COMMUNITY, however, has a rich history dating back to the early 1800s.
Sand Rock doesn’t have a post office (but it does have a Zip Code!), nor does it have a supermarket, clothing shop, or hardware store. It does have a fine school, which began as a log cabin and is now a beautiful modern multi-building complex. Church buildings also stand as a testimony to the community’s strong faith, along with a friendliness that has stood since the day Sand Rock was named by Grandfather Brindley.
Sand Rock began when two brothers were traveling the old Indian trail from the Carolinas to Mississippi. One of the brothers was Euclid V. Brindley’s grandfather. He liked the top of Lookout Mountain, on the trail between Leesburg and Collinsville, where the two brothers stopped to rest beside a spring. One of the brothers moved on, but Grandfather Brindley stayed.
The exact date the two brothers stopped on Lookout Mountain is not recorded. But, according to local historians, the Brindley who stayed to rear a family here looked at the huge sand rocks, crumbled some between his fingers, and exclaimed, "Sand Rock."
Sandstone is a very common sedimentary rock and perhaps the best known sedimentary rock. It is formed in many environments. Just about anywhere there is water, whether frozen or not, in a river or ocean, there is a chance to form sandstone. Even where there is no water as in a desert, there is sandstone formation under foot
As the name implies, sandstone is composed of sand. That seems easy enough. However there are a few other things to consider. What is sand? Sand is characterized by any grain that is 0.1 mm to 2.0 mm in size. Any smaller grain size and you have a shaleor siltstone, any larger and you have either a conglomerateor a breccias. The grains can be composed of individual crystals of various minerals such as quartz or feldsparor even be a sand-sized fragment of another rock such as a granite or slate.A magnifying glass is usually sufficient to distinguish the general composition of a sandstone. How a sandstone formed is usually important to geologists and the minerals or rocks that are in it are critical to determine where the source of a sandstone's composition came from. The roundness of the grains is also important in determining the amount of distance the sand has been tumbled before deposition or the closeness of the source to the final deposit. The lack of fine grains and mud in a sandstone indicates a relatively high energy environment of deposition such as the wave action on a beach, the wind sweeping across a sand dune field or the rush of a river current.
The grains are important to geologists and so are the minerals that cement them together. Sandstone cements can influence the durability, color, porosity and usefulness of the stone. Normal cementing agents include calcite, quartz(silica), clays and gypsum. Silica cemented sandstone is very durable and hard. Calcite cemented sandstone is subject to acidic dissolution and is more easily eroded. Clay and gypsum cements, which are soft minerals, tend to produce much softer sandstone and the sand can sometimes be rubbed off in a person's hands.
The cementing agents also affect the porosity of a sandstone. When the initial sand is first deposited there are lots of open spaces or pores. Water, for instance, flows right through sand due to all the pores. But as the sand turns into rock, the cement can fill in these pores making the sandstone less porous and less able to allow water to move through the rock. Generally sandstone is a very porous rock as rocks go and will have substantial pore spaces. Sandstone is the ideal rock for ground water and will house substantial aquifers. Petroleum also is a fluid that flows through sandstone and sandstone is also the best oil reservoir.
Iron oxides, manganese oxides and other impurities can cause bright and contrasting colors in sandstones. These colors are what gives sandstone its unique character and ornamental desirability. The colors range from bright whites, reds, yellows, oranges and even purples and greens. Colored sandstone is usually intricately banded in multiple colors which enhance its aesthetic appeal.
Sandstone's banding is due to layers of sand that are deposited with differing characteristics. Sandstone is formed in many deposits that are episodic in nature and the resulting layers can be very different from previous layers. Sometimes the sand is courser or finer than the previous layer and this difference causes the banding. Dunes and ripples of sand can cut across earlier deposits and cut off those earlier bands with bands of their new.
Sandstone deposits can be a beautiful part of the natural environment and apart of the breath-taking views at many natural parks and preserves. The sandstone deposits of the the Grand Canyon, Zion, Bryce, Mesa Verde, Arches, and Red Rock National Parks to name a few in just the USA provide millions of visitors spectacular views.
Mined sandstone can be cut, polished and carved for many uses. It is used as ornamental rocks for buildings, monuments, grave stones, bookends, beverage coasters, tiles and many other possible uses. Sandstone can also provide silica for glass production.
Some mineral ores are found in sandstone. Uranium can concentrate in uranium minerals in sandstone deposits and many uranium ore bodies are the result. Heavy minerals such as rutile, gold, diamonds,and others can be found in sandstones from prehistoric placer deposits that are now worked for their economic value.
What Sandstone Says
The sand grains in sandstone give information about the past:
· The presence of feldspar and lithic grains means that the sediment is close to the mountains where it arose.
· Detailed studies of sandstone give insight into its provenance—the kind of countryside that produced the sand.
· The degree to which the grains are rounded is a sign of how far they were transported.
· A frosted surface is generally a sign that sand was transported by wind.
Various features in sandstone are signs of the past environment:
· Ripples can indicate the local water currents or wind directions.
· Load structures, sole marks, rip-up casts and similar features are fossil footprints of ancient currents.
· Liesegang bands are signs of chemical action after burial of the sand.
The layers, or bedding, in sandstone are also signs of the past environment:
· Turbidite sequences point to a marine setting.
· Crossbedding (truncated, tilted sandstone layering) is a rich source of information on currents.
· Interbeds of shale or conglomerate may indicate episodes of different climate.
· Depending on the mix of matrix and cement, sandstone may have a wide range of color from nearly white to nearly black, with gray, brown, red, pink and buff in between.
Some uses of sandstone
Sandstone is a rock type which has many uses. Strongly cemented sandstone is used as a building material all over the world where sandstone is readily available. Sandstone is often used in house building and fireplaces.
Crushed sandstone (as sand) is a common filling material in road construction and sand is a principal component of concrete. Pure quartz sand is a source of silica which is used to make glass, carborundum, and semiconductors. Some strong sandstones with sharp grains (gritstone) are good for grinding.
Special types of crushed sandstones are used in agriculture as a soil conditioners (lime sand) or fertilizer (glauconite sand). Chemical industry uses sandstone because it is very resistant to most acids (however, this is true if the sand is really almost pure quartz sand). Last, but not least, sandstone, because it is porous, is by far the most important reservoir rock of ground water and hydrocarbons (crude oil and natural gas).
To obtain credit for this Earthcache, send me the answers to the following questions via e-mail with the title THE ROCK at the beginning of your e-mail. Failure to do so will result in the deletion of your log and find of this Earthcache.
1. In your opinion, how long, thick, and wide do you estimate this outcropping to be?
2. As you observe this outcropping, you can determine various features of its past environment.
· Name the 2 types of sand grains due to the location of the outcropping.
· Did you observe a frosted surface on this outcropping? If so, why?
· During your observation did you notice any ripples in the outcropping? If so, why?
3. There are many colors that make up a mixture in this outcropping. Name all the colors you see present and which color is more prominent than the rest?
4. The way this stone cements together can influence the durability, color, porosity and usefulness of the stone. Name the 4 normal cementing agents and based on your observation, which one or ones do you think are cementing this outcropping together and why?
5. Name 3 or more uses that this outcropping of rocks are used for in our society today.
6. Even though it is not required, a nice photo of you and your gps with the outcropping in the background would be a nice keepsake for you and a memory to remember! Thanks for visiting THE ROCK!