LINCOLN TOMB
Within the walls of this stunning granite monument is the final resting place of Abraham Lincoln, his wife, Mary and three of their four sons. Designed by famed sculptor, Larkin Mead, and completed in 1874, this landmark is nestled in Oak Ridge Cemetery.
At the entrance to the Tomb itself, there is a bronze bust of Mr. Lincoln where visitors stop to rub the nose of the statue for good luck.
The tomb’s exterior is constructed of dressed granite from Quincy, MA and rises to a height of 117 feet. Four flights of granite steps lead to the terrace, which has a cordon of thirty-seven shields, each bearing the name of a state that made up the Union at the time of the original construction.
On the face of the pedestal is a bronze plaque ornamented with a coat of arms of the United States and representing the Constitution. A fragment of the ancient Roman Servian Wall (built in 578 B.C.) is attached to the obelisk, a gift from the people of Rome to President Lincoln.
GRANITE
Granite is a rock formed by the slow cooling of magma at great depths in the Earth's crust. This extended cooling allows large crystals to form, resulting in the characteristic crystalline texture of granites.
There are two simple rules to assess the quality of granite:
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Grain Size: In general, the larger the grain size of the granite, the lower its hardness and it is easier to be crumbled. This is particularly evident in older granites, such as those used in Roman and Renaissance buildings.
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Color: The darker the granite is, less proportion of quartz it has, and therefore, it is harder.
Granite is composed of three minerals: Quartz, which can be transparent, white, or gray; Feldspar, which comes in white, pink, red, yellow, brown, green, and gray; and Mica, along with other minerals, typically black. Each of these mineral groups weathers according to its own chemical properties.
WEATHERING
The natural process of breakdown and erosion of this igneous rock is called weathering, contributing to both physical and chemical changes in the rock over time. The most common weathering types are the following:
- THERMOCLASTY: Breaks occur due to rapid temperature variations between day and night.
- BIOCLASTY: Plants and living beings are capable of breaking rocks.
- HALOCLASTY: Water and salts circulate through the pores and fissures of the rock, precipitating inside them.
- CRYOCLASTY: It occurs when the water within the pores and fissures freezes.
- HYDROLYSIS: Hydrolysis is the chemical weathering of minerals by a mildly acidic water that forms when rains dissolves trace gases in the atmosphere.
TASKS
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Do not post the answers to your log. You do not have to wait for the reply before you claim this, though if something is noticeably incorrect with your answers, we will reach out directly to resolve it.
1. What colour grains can you see in the granite?
2. To the touch, is the granite of the tomb smooth or rough?
3. According to your previous answer. What type of weathering can you appreciate in the granite?
4. How much does the ashlar of the coordinates weigh (The block containing the bust of Lincoln)?
