Masslite Quarry, Plainville, Norfolk Co., Massachusetts, USA

Ref.: Rocks & Min.: 21:754. A slate and concrete aggregate quarry located about 1 1/4 mile NW of Plainville. Started about 1935. Workings were 700 feet long by 60 feet wide and 40 feet deep (or high at the face). Mostly a location for Carboniferous (Westphalian C) plant fossils and trackways. Many undetermined sulphates are found in a thick coal seam.

There are multiple levels, and the level searched is crucial as to which type of fossils will be found. The level that is at about the same elevation as the entrance contains white plant imprints on dark gray rock. These rocks are not hard to find but are definitely the minority, and are found in the rock piles leaning against the quarry wall at the opposite side of the entrance. White strip-like calamites leaves are very prevalent and are often exposed, a perfect flag for a fruitful rock worth splitting. Directly above this plant area, but at the top level, there are light gray or light brown (oxidized surface?) rocks that contain rather small footprints of reptiles and amphibians. These rocks are also in a pile leaning against the quarry wall, but unlike the plant rocks, are the only type present. Most levels, especially all those beside the top one, contain interesting quartz crystals as well as other inorganic minerals.

Plants and footprints are the most common fossils found, but insects among others have been reported. The plant fossils are especially interesting because the rock is fairly highly metamorphose, causing the plants to be white and the rocks to often contain graphite or quartz crystals. The footprints are in more standard sedimentary rock and are often somewhat difficult to discern. One must remember that this quarry is still actively mined, so it is off limits except for Sundays and likely holidays. The walls are sheer and rocks can fall, so keep a safe distance from them.