190 PROCEEDINGS OF THE ACADEMY OF [1892. 



mineral when immersed in water decrepitates with considerable 

 noise. This locality is in East Bradford township, and amethysts are 

 found in nearly all the fields within half a mile of it. 



Half a mile northwest from the Birmingham quarry is Osborn's 

 Hill, in which a mine was opened about the year 1835 for manga- 

 nese, and half a ton of the black oxide taken from a depth of thirty 

 feet. The vein stone was massive mauganesian garnet containing 

 crystals of yellow sphene. Tourmaline, in small crystals in quartz, 

 occurs abundantly, also orthoclase crystallized, on the west side of 

 the hill. 



Very few minerals have been found in the hornblende rocks of 

 Chester County, the principal ones being zoisite at the old water 

 works in West Chester, noAV inaccessible ; labradorite, sphene and 

 sunstone, the latter of great brilliancy, were found at Lamborn's 

 mill, one-half mile southeast of Kennett Square ; epidote crystals 

 occurred loose in the soil one mile south of the borough ; sunstone 

 is also found near Fairville. One-half mile north of Fairville, on 

 the farm of the late William Dilworth, muscovite crystals occur by 

 the hundred in the soil northwest of the house, near the woods. 



One-half mile south of Pennsville, on the farm of Jacob Swayne, 

 there is a large deposit of white quartz containing a few crystals of 

 feldspar, and large crystals and plates of muscovite beautifully 

 marked by magnetite and containing compressed ci'ystallized quartz, 

 suitable for the microscope. Some almost perfect crystals from this 

 place measured eighteen inches by twelve or more. A large quan- 

 tity of merchantable mica was obtained. 



In quarrying for limestone in Chester Valley they occasionally find 

 openings or small caves filled with stalagmites and stalactites, some 

 of the latter being a foot or more in length ; a few brilliant crystals 

 of pyrite are sometimes found in the limestone, also fluorite and 

 quartz crystals; at the Pennsylvania Railroad quarry. East Cain 

 Township, ankerite. 



In the limestone on the Brandywine Creek, about a mile above 

 Chadd's Ford, occurs chondrodite, the only locality of this mineral 

 in the region. 



The quarries in West Bradford Township, known as the Poor- 

 house quarries, were opened nearly one hundred years ago and are 

 in a magnesian limestone; in it are found the following minerals: — 

 chesterlite, quartz crystals, rutile in needle-like crystals, some trans- 

 pai'ent and of a dark ruby color ; tremolite and a yellow damourite 



