Sunset Red on the Grove EarthCache

This is an Earthcache – as such, there is no physical cache. Instead after examining the specimen at the posted coordinates you will answer 3 questions and message me the answers. The Lyndon Baines Johnson Memorial Grove on the Potomac is open year round from 6 am to 10 pm. For more information on park rules, hours of operation, or to learn the history of the park please visit this LINK to go the the National Park Service Lyndon Baines Johnson Memorial Grove on the Potomac webpage. Permission for this cache placement was given by the National Mall & Memorial Parks Division of Permits Management.

The focal point of the Lyndon Baines Johnson Memorial Grove is a tall block of sunset red granite. It was selected to symbolize the energy and personality of the 36th President of the United States. The monolith stands 19 feet high and weighs 43 tons.

It was quarried in Texas just 35 miles from the LBJ Ranch from Granite Mountain, which is a solid dome of pink granite rising over 860 feet one mile west of Marble Falls, Texas. Since quarry operations began in the late 19th century, the distinctive pink-red colored rock has been used in the construction of the Texas State Capitol in Austin.

Granite is an intrusive igneous rock that begins as a molten liquid state that solidifies as it cools. The texture is now determined by the rate in which it cools. The large mineral crystals in granite are evidence that it cooled slowly from molten rock. That slow cooling occurred beneath the earth's surface and required a long period of time. Granite which cools closer to the earth's surface as when it is exposed to air or water, cools more rapidly and the result is a granite with crystals that are smaller.

Granite comes in a wide variety of colors--greens, blues, reds, browns, yellows, black, white, gray, and more. The pink color of this monolith is from the large amount of orthoclase in the stone. Orthoclase is a feldspar mineral and it is most widely known as the pink feldspar found in many granites. It is one of the most abundant rock-forming minerals of the continental crust. As the amount of orthoclase feldspar increases in the granite, the color becomes pinker.

LOGGING REQUIREMENTS:

To log this Earthcache: Read the geology lesson above. Answer all four questions posted below. Answers can be sent via e-mail or messenger contacts on my Geocaching profile within a reasonable time. Group answers are fine, but please include the members of the group you are with. NOTE: This cache page was edited on 4/4/2023 to give a more streamlined earthcache lesson. Only the images and questions have changed.

QUESTION 1. What kind of stone is granite? (CHOOSE ONE)
A) Sedimentary
B) Igneous
C) Metamorphic

QUESTION 2.Using the mineral chart in the above lesson, which mineral makes up the majority of color of this granite?

QUESTION 3. What is the texture of the pink granite monolith?
A) Pegmatitic: A texture is one in which the rocks crystals are about 1” long to larger.
B) Phaneritic: A rock that has crystal grains large enough to be distinguished with the eye.
C) Aphanitic: This texture consists of extremely small crystals

OPTIONAL PHOTO: Posting a photo that readily indicates that you (and anyone else logging the find) are at the location.

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