Mineral specimen displays at museums may seem unattainable to the average person, but there are many places around Chester County where you can find them yourself. I decided to investigate some nearby sites– and was pleasantly surprised with what I found.
The Avondale Quarry near the intersection of Route 41 and Old Baltimore Pike opened in the 1920s, with plenty of building stone, flagstone, sand and aggregate over the years. Minerals such as garnet, biotite and muscovite mica, black tourmaline, graphite, marcasite and rutile have been reported at this location. Most people know mica as the glittery, sheet-like mineral which peels off in flakes, but are not aware of its varied applications. It has superior thermodynamic properties, providing stability in the presence of electrostatic fields. It is commonly used in joint compounds for drywall, various coatings, roofing shingles and concrete blocks. Rutile is a processed an opacifying agent, titanium dioxide, of which Du Pont is the world’s largest producer.
People like looking at crystals– and they can be found at Avondale in large quantities. Garnet, a deep, ruby red, semi-precious gem is frequently found in metamorphic rocks of Chester County. Black tourmaline crystals are also abundant, present in a feldspar/quartz/mica framework within pegmatite veins; intrusions of molten rock which cooled near the surface millions of years ago.
To the southwest, the Nottingham area holds copious amounts of both feldspar and serpentine at the State Line and Goat Hill mines, along with quarry deposits in the local park. Many houses have an olive green serpentine framework. Colonists used this stone in buildings for both endurance and beauty. Feldspar, a chalky, off-white to pink mineral, is commonly present in granite. It is ground into a very fine powder and included as an abrasive agent in toothpaste and is used in ceramics, paint fillers, plastics and rubber. Feldspar even helps us see things better. Alumina from feldspar improves the hardness and durability of glass, adding to its resistance to chemical corrosion.
Ron Sloto’s book The Mines and Minerals of Chester County lists 1808 as the first printed reference to minerals from this area. His book provides a wonderfully detailed description of the enormous variety of riches present, replete with color pictures of mineral specimens, topographic maps and mine diagrams.
There are numerous places to collect minerals around the county. Forty-nine of our 56 townships hold quarries or abandoned mines containing worthwhile specimens. Be sure to ask for permission before treasure-hunting on private property and be careful–these sites can be hazardous. You don’t have to be a geologist to find them–just take a hike and keep your eyes open.