This is an earthcache so there isn’t a container to find but instead you discover something about the geology of the area. To log this cache as a found, you will explore the location and then provide answers to a few questions. The earthcache is winter friendly but, if there is snow, you may need to brush snow off the granite block in order to view the granite to answer the questions.
Biddeford quarries
Clifford Park was once home to granite quarries which were part of a huge export industry in Biddeford in the 1800s into the mid-20th century. The earthcache will bring you to the remnants of one of Biddeford's granite quarries in in the park where you will see massive stone blocks scattered around the ground along the top of the quarry.
Mining the granite was a labor intensive task. There were many different means used to mine the granite at a quarry. One means is heating by fire and then splitting by impact with an iron ball. Another means is by using existing cracks or drilling holes and then driving iron bars into the crevice. You can still see the remnants of drill marks on some of the blocks in the area.
Since granite is heavy, it is important that low-cost transportation is available. Biddeford is located near the Saco River and the Atlantic Ocean so barges and schooners were used to transport the granite.
Biddeford granite was used in many places within and outside of New England. Some examples of where it was used are in the rebuilding of the breakwaters at the mouth of the Saco River, in construction of the military forts near Portland, in the Lincoln monument in Illinois, and in the foundations of the Brooklyn Bridge.
Biddeford Granite
Three major rock types dominate the bedrock of southern Maine: metamorphosed sedimentary rock, intrusive igneous rock, and thin dikes of basalt. This earthcache will explore the igneous rock found in Clifford Park which is part of what is called “Biddeford Granite.” The granite rocks follow two main granite veins which cross the park East to West. The image below shows a portion of the Biddeford area which contains the main body of Biddeford Granite. The area is roughly oval-shaped, approximately 6 miles by 10 miles across.
Granite definition
The basic definition of granite is it is an igneous rock that is composed mostly of feldspar and quartz with trace amounts of micas and amphiboles that are present in crystals large enough to be visible with the unaided eye.
What are igneous rocks?
Igneous rocks are formed by high heat and pressure from molten rock material called magma. As the magma cooled, it solidified into granite. Some form below Earth's surface. Some form on or above Earth's surface. These two basic types of igneous rocks are called intrusive or exclusive. Intrusive igneous rocks crystallize below the Earth's surface, and the slow cooling that occurs there allows large crystals to form typically the size of a pea. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form smaller crystals some as small as the head of a pin.
The size of the crystals in granite determine how the granite is used. Monumental granite must be fine grained, with crystals the size of a pin head, to allow fine carved details and to accept a mirror-like polish. Building granite is more coarse-grained with large crystals which provide strength.
Granite composition
Granite is composed primarily of feldspar and quartz with smaller amounts of mica and other minerals. Biddeford granite comes in many colors and textures, with each quarry yielding its own variety of stone. The mineral composition of granite is what gives it a red, pink, gray, or white color with dark mineral grains visible throughout the rock.
- Feldspar
Granite's principle element is feldspar. In addition to contributing to strength and hardness, feldspar primarily determines granite's color, resistance to discoloration and decay, and ability to receive a polish. Feldspar minerals are usually white, gray, pink or reddish in color.
- Quartz
Quartz contributes to granite's strength, hardness, and luster, and acts as a cement binding all the elements together. Quartz will usually be a transparent mineral that is colorless or gray in color.
- Mica
Mica (mostly white muscovite and black biotite) is present in smaller amounts. The relative amounts of white and black mica are an important factor in the color of the granite. If white mica predominates, the granite will be light-colored, and if the black predominates, the granite will be dark. If the white and black occur in roughly equal amounts, the granite will be speckled.
Earthcache questions
To get credit for this earthcache, you will need to send to me the answers to the following questions by email or Message Center. Please include the name of the earthcache in your message. You don't have to wait for a response from me after you send the answers.
- Do you think the granite at this location is intrusive or extrusive? Explain why.
- What are the colors of the granite seen here?
- For each color seen in the granite, explain which mineral you think is contributing to the color.
- Include a photo of you and/or your GPSr/phone at ground zero.