In April, Bay Buddies looked at the geological provinces of the Chesapeake Bay watershed. Now it’s time to get down to the nitty gritty. Test how much you know about some of the watershed’s rocks and minerals by matching them with their descriptions. For extra credit, which are minerals and which are rocks?
1. This is the fine black sand we see along Atlantic Coast beaches. Despite its color, one of its principal uses is as an ore of titanium, the metal used to make white paint “white.”
2. This is created when fine-grained shale, or mudstone, is metamorphosed, or exposed to great pressure, heat or chemicals deep within the Earth’s crust. It was once used to make blackboards.
3. This is sometimes called “slickenite” because of its polished, slippery surface. Its high manganese content and lack of lime and alkalies makes soils containing this substance infertile, resulting in scant, if any vegetation.
4. This is formed by the metamorphism of sandy shale and has a thinly layered, foliated appearance. The shiny flakes in the layers are mica. It may also contain quartz, feldspar and garnet. Because it often splits along its foliation, it is not generally used in construction, although it may be used as flagstone or for the facing of exterior walls at ground level.
5. This forms when limestone has been metamorphosed. Heat creates its uniform crystal size, while pressure helps to develop its distinctive streakiness. Because of its strength, as well as its beauty after it has been highly polished, it is often used in construction or for statuary.
6. This extremely common substance is a popular source of gemstones. In its transparent form, it is known as rock crystal. Its purple and yellow forms are called amethyst and citrine, respectively. It is a common grain in many rocks as well as beach sand.
7. This is usually created on ocean or sea floors and contains fragments of coral and sea shells. It is noted for the many varieties of fossils found in its layers. It is used to make concrete and in iron– and steel-smelting operations.
8. This forms slowly by crystallizing from molten rock at great depths beneath the Earth’s surface. It is brought to the surface during the creation of mountains and is often what is exposed after the other rocks and minerals have eroded away. This hardness, and its beauty after it has been highly polished, has led to its being widely used in construction or for monuments.
9. This is composed of fine-grained clay sediments deposited on the bottoms of lakes and oceans. It splits easily into flat fragments parallel to bedding. Some varieties contain many fossils and ripple marks. It is used to make pottery and bricks.
10. This forms when molten rock is suddenly thrust to the Earth’s surface or is intruded into cracks near the surface. It often contains round cavities that were created by bubbles of trapped gas. It is sometimes used as an ornamental stone.
11. This is formed by small grains of rocks — mostly quartz — cemented together by silica or calcite during the compaction of beaches, floodplains or deserts. It feels gritty to the touch. Its brown variety is the “brownstone” used for buildings in the Eastern United States.
12. This is formed by sandstone or granite plutonic rock that his been exposed to extreme pressure. It is noted for its alternating light and dark bands. While it appears similar to schist, its components may have a different chemical composition, and this substance forms under higher temperature and pressure conditions. It is used to decorate interiors and exteriors of buildings.
1. D 2. K 3. I 4. H 5. F 6. L 7. E 8. C 9. J 10. A 11. G 12. B
Minerals: D & L