History of Chester County, Pennsylvania, with genealogical and biographical sketches, Part 121

Author: Futhey, John Smith, 1820-1888; Cope, Gilbert, 1840-1928
Publication date: 1881
Publisher: Philadelphia, L. H. Everts
Number of Pages: 1162

USA > Pennsylvania > Chester County > History of Chester County, Pennsylvania, with genealogical and biographical sketches > Part 121

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"To the north of the great. limestone valley, and em- bracing more than two-thirds of the area of the northern half of the county, is another large belt of the gneiss forma- tion:" "The junction of this with the northern margin of the primitive or auroral limestone of the Great Valley is concealed by the overlapping of the sandstone of the Valley Hill." (Formation I. of the State survey.) " The northern gneiss-belt of Chester County commences at the northeast part of the county by a very narrow zone, after which it expands rapidly in a south west direction, embracing the northern part of Charlestown township, the southern part of Schuylkill and East Pikeland, and the whole of West Pikeland, West Vincent, Uwchlan, East and West Nantmeal, East and West Brandywine, and parts of Honey- brook, West Caln, and Sadsbury, where it passes into Lan- caster County, " having French Creek for its northern boundary, and the base of the North Valley Hill for its southeru limit." "The northern margin of this gneiss helt, from Valley Forge to the eastern extremity of the Welsh Mountain, passes beneath the middle secondary red sandstone (Formation V.), and on the northwest beneath the older sandstone ( Formation I.), of the Welsh Mountain itself." The structure of the northern gneiss-belt is more coarsely crystalline than that of the southern part of the county ; the predominant constituent is feldspar, and the rocks contain more hornblende and less mica than the latter.

In numerous places in the townships of East and West Pikeland, East and West Vincent, and Uwehlan numerous beds of hematitic iron ore and carburet of iron, or plum- bago, exist. Small trap dykes often occur in the vicinity of these ore-beds. Several small beds of highly crystalline limestone are also found in this gneiss-belt. All the rocks and their included minerals of this part of the county ex- hibit the effects of a greater amount of heat than those of the southern part. The dip of the rocks of the northern guciss-belt, together with the included beds of iron and limestone, is in conformity with those of the southern part of the county, before described ; in the southern part of Schuylkill township, near the junction of the gneiss with the middle secondary, or mesozoic red sandstone, but within the former several parallel lead-bearing veins or lodes occur. They are found filling fissures in the rock, transversely to

the general direction of the strata in which they occur. All these mineral injections or lodes have a general north- east and southwest direction, and they vary from a few inches to upwards of two feet in thickness. The dip of these veins is southeast, in some instances approaching the perpendicular. Of all these lodes the Wheatley mine, in Charlestown township, is the most celebrated for the beauty and variety of its mineral products, the various salts of lead being the most magnificent of any ever obtained in lead-mining, and unequaled by anything to be seen in the cabinets of Europe. The reputation of this mine for the beauty and variety of its minerals for many years rendered it the Mecca of specimen-hunters.

" Somewhat to the north of the centre of the county, and extending across it by a narrow zone, varying from one to three miles in width, is the primitive or auroral lime- stone which forms the Great Valley. Entering it from the adjoining county of Montgomery, where it commences near Willow Grove, the formation extends in a northeast and south west direction, occupying the northern part of the township of Tredyffrin, East and West Whiteland, the central parts of East and West Caln, Valley, and the southern part of Sadsbury, where it passes into Lancaster County. On the north it is bounded by the southern base of the Valley Hill, which consists of white sandstone (Formation I.); its southern limit is the northern base of the Talc Slate Ridge, or South Valley Hill, which also extends across the whole breadth of the county." In many places where it is in contact with the tale slate it is slaty, and is strongly. marked by the igneous action which upturned the latter, and which probably destroyed all traces of organic struc- ture in the limestone. If we except a few instances in the neighborhood of the Steamboat, which some geologists think may resemble large fucoids, no trace of organic remains is to be found. The texture is compact, slightly crystalline or granular, and sometimes slaty, and the colors vary from blue to white, which are often alternated in the same bed. "The dip of the strata is very uniform, being south at an angle of 60° to 65°." Several beds of iron and plumbago occur in this formation. The ores of the former are silicious but rich, while the latter, in consequence of their proximity to the tale slate, are talcose or earthy, and unfit for the purposes to which this mineral is applied.

" The next formation in the order of superposition is the extensive slates and sandstones which constitute the lowest member of our older secondary or Appalachian rocks (Formation I.) of the State survey." "The principal ridges of this formation in Chester County which have escaped the general denudation which has removed so much of the secondary rocks from the southern part of the State are the Welsh Mountain, Coppermine Ridge, and the North Valley Hill, besides two or three other minor hills hercafter noticed." The most extended belt of this formation, called the North Valley Hill, is a long, elevated ridge, of almost uniform width, bounding the northern margin of the primitive or auroral limestone, and conceals the junction of the latter with the northern gnciss-belt." The white sandstone formation emerges from beneath the overlapping of the mesozoic, or middle secondary sandstone (Formation V.), at the hill near the

R.L Stopfer. En!

"THE PROSPECT HILL FARM." RESIDENCE OF JOHN JOHNSON. WILLISTOWN.

" MAPLEWOOD

FARM "

RESIDENCE OF JOSEPH I. STUBBS EAST NOTTINGHAM CHESTER CO. PA.

437

GEOLOGY OF CHESTER COUNTY. .

Valley Forge upon which Gen. Washington encamped during the memorable winter of 1777, known as Mount Washington, and runs in a westerly direction to Bart township, Lancaster Co." The strata within the county varies from 1000 to 2000 feet in thickness, and con- sists of three divisions, known as the upper, middle, and lower primal slates. " East of Coatesville very little of the primal slates are found, but when Coatesville is reached the slates exceed the sandstone strata in thick- ness, the upper members of the series being 700 fect thick, while the sandstone is but thirty-five feet. From this point the primal sandstone is surmounted by the upper, middle, and lower slates, in descending order, until the North Valley Hill joins Coppermine Ridge. "The cen- tral crest of the Valley Hill consists of sandstone, which is the middle member of the series, the northern flank being occupied by the lower primal slates, and the southern flank by the upper," showing that the chief denuding force which cut down this hill came from the north. Be- tween Downingtown and Valley Forge we meet with faint impressions of a few fucoids, and near the Valley Hill the Scolythus Linearis is found. The impressions of fu- coids are also seen near Trimble's mill, where the road from West Chester to Lionville crosses the Valley Hill, and where the hill has been cut down almost to the gneiss. A beautifully-preserved vegetable fossil may be seen on a stone in the mill-wall, near the door. " The Welsh Moun- tain, which is another ridge of these sandstone formations, is situated at the northwest extremity of the county, and bounds the northern margins of the townships of West Nantmeal and Honeybrook. It runs in a southwestern direction, and extends from the village of Springfield, in West Nantmeal, to the county of Lancaster, where it ter- minates in Earl township. Southwest from this is another ridge, known as Coppermine Ridge, which originates west of the village of Sadsbury, and passing southwest through this and the adjoining township of Sadsbury, also enters Lancaster County, and terminates on Big Beaver Creek. Three or four smaller hills of this formation occur in the county, one of which is in the lower part of Uwchlan township, another north of the Friends' meeting-house in Londongrove township, and a still larger one south of the village of Chathanı." A portion of this formation may also be traced on the West Chester and Wilmington road, north of Dilworthtown, a quarry of which exists on John Woodward's farm. This formation is supposed at one time to have covered the surface of Chester County to the depth of several thousand feet, and at the known rate of a foot a century in which such deposits occur, it would have required several thousand years for its completion. The lower layers of the Potsdam sandstone are more solid and compact than the upper. This was probably the re- sult of two forces, the lower receiving the greater amount of heat from its contact with the gneiss, as well as the pressure from the weight of the superincumbent rock. In the upper series of these sandstone rocks we find ripple- marks, mud-cracks, worm-burrows, and occasionally the track of a marsupial animal, showing that the continent at that period was slowly emerging from the occan. Within this county, however, the fossils are confined to the fueoids

and the Scolythus Linearis. "The general direction of these sandstone ranges is northeast and southwest, and the dip of the strata is southeast, at an angle of 70°. The thickness of the several members of the strata varies from 100 to 650 fcet each."

" The next strata in order is the secondary limestone (For- mation II.) of the State survey, which forms Pequea Valley. This formation enters West Caln township on its western border, and then runs east to join Coppermine Ridge. On its northern and eastern border it overlaps the gneiss, and on the south it is in contact with the sandstone of Mine Ridge (Formation I.) In Honcybrook township there is another small bed of this limestone, sitnated at the base of a ridge of Formation I. The dip of Formation II. is south- cast at an angle of 45°, and the thickness is supposed to be about 6000 feet."

That part of Chester County lying between the Schuy !- kill River and French Creek is occupied by a portion of the mesozoic or red shale formation (Formation V. of the State geological survey), and is a part of a belt which ex- tends from New York to Virginia, and which at one time was part of a wide estuary that floated the sediment which went to form these rocks, " the shore-line of which is still visible in the valley of the French Creek, which is marked by a succession of hills that prevented the waters from flowing south." " The formation consists of layers of dark, reddish-brown sandstone, alternated with soft slates, calca- reous shales, and coarse conglomerates. It is made up of angular fragments of quartz and feldspar, together with por- tions of the adjoining gneiss rocks, the whole being cemented together by a reddish-brown argillaceous matter, which im- parts to this. formation its peculiar red color." The town- ships embraced by this formation are the castern half of East Pikeland, East Vincent, Warwick, and North, East, and South Coventry, together with a large part of Schuyl- kill.

" The southern margin of this strata overlaps the gneiss of the northern part of the county, but after passing into Berks and Lancaster Counties it is often in contact with Formations I. and II. The dip of the strata is north to north- west at an angle of 15° to 25°, and its thickness is about 2000 fect." Numerous trap dykes occur in this and adjoining strata of the northern part of the county, which appear to have been injected through the rocks in a state of fusion ; the undulations of the earth's crust, which was accompanied by intense heat at this period, produced numerous fissures in this and adjoining strata, which are now occupied by veins of iron, copper, lead, and plumbago, chiefly the former, for which this part of the county is celebrated. The iron is usually " found in the folds or troughs of the gneiss, and is derived from the red sandstone which has yielded up its iron by the process of filtration, which has been deposited in the positions where it is now found, and where it has been modified by the action of heat, which is manifest in the geodes of iron containing beautiful irides- cent stalactites."

The several veins of lead and copper which border the junction of the gneiss and new red sandstone, in the neigh- borhood of Phoenixville, are true mineral lodes or injec- tions, and were deposited contemporaneously with the move-

438

HISTORY OF CHESTER COUNTY, PENNSYLVANIA.

ment of the earth's crust which dislocated the rocks in this part of the county. The rocks of the new red sandstone, in the neighborhood of Phoenixville, are often found to contain immense numbers of the exuviæe.of the genera Cypris and Estheria, small fresh-water crustacea, and in the neighborhood of Valley Forge large coprolites are found, showing that immense fish, probably Ichthyosaurus or Ple- siosaurus, visited this vast estuary. Two species of lingula are also found in the rocks above Phoenixville, covered in some instances by crystallized quartz.

The Keuper slate is third in the series into which geolo- gists divide the mesozoic or new red sandstone. This strata is well developed in the cutting of the Black Rock tunnel of the Reading Railroad, at Phoenixville, in this county. Through the persistent efforts of Charles M. Wheatley, Esq., many fossil remains, both animal and vegetable, have been rescued from the ancient bone-bed of these hard slates, and have been made known to science by Mr. Wheatley and Professor E. D. Cope. Among these are the remains of the Labyrinthodon, together with those of shark, and other large fish possessing formidable teeth, whose carcasses, after death, were swept by the tides into this cove of a great estuary, or visited it while living.

MINERALOGY.

The best exhibit, perhaps, which we can present of the rocks, minerals, and ores found in Chester County is the following table, arranged by George G. Groff, M.D., Natu- ral Science Professor in the West Chester, Pa., State Nor- mal School :

THE MOST COMMON MINERALS, ORES, AND ROCKS OF CHESTER COUNTY, PA.

MINERALS.

QUANTZ. - Hardness, #7; white, red, blue, yellow ; lustre, glassy ; brittle; forio, six-sided crystals and massive; breaks irregularly ; composition, siliea (SiO2) ; comicon in all parts of the county; the most abundant of all our minerals; cuts glass readily ; infusible.

CHALCEDONY .- Hardness, 7; all colors ; lustre, waxy ; tough ; form, massive, no crystals; has a curved fracture; composition, siliea; eom- men on serpentine barrens, and in Warwick ; a variety of quartz, often translucent, and in beautiful forms.

JASPER .- Hardness, 7; red, yellow ; lustre, earthy ; tough; form, massive; has a eurved fracture ; composition, siliea and elay ; common en barrens, West Goshen ; a variety of quartz, made impure by presence of elay.

CALCITE .- Hardness, 3; white, all colors ; lustre, glassy, pearly ; brittle ; form, erystals, rhombs, prisms ; eleaves inte erystals; eompo- sition, carbonate of lime; common in mines and limestone quarries; this is limestone purified and crystallized, same as marble.

DOLOMITE .- Hardness, 4; white, yellow, red ; lustre, glassy, pearly ; brittle; form, crystals, rhombs, massive; eleaves into crystals; eom- position, carbonate of lime and magnesia ; found in mines, and lime- stone south of Great Valley ; caleite and magnesia; both effervesce in neids.

SERPENTINE .- Hardness, 3-5; shade of green ; lustre, feeble ; brittle; forio, massive, no erystals; breaks irregularly; composition, silica, magnesia, water; found in barrens, south and western part of county ; distinguished by its green color and soft, grensy feel.

TALC .- Hardness, I; white, green ; lustre, pearly, greasy ; flexible; form, in seales and plates ; splits into thin leaves; composition, siliea, magnesia, water; common with serpentine; distinguished from mica by its greasy feel, and is not elastic as mica.

HORNBLENDE .- Hardness, 5-6; brown, black ; lustre, pearly, glassy ; tough ; form, erystals, blades, scales; eleaves in smooth blades ; com- position, silica, magnesia, iron, ca .; found in gneiss rocks, and at Knauertown; the dark mineral in our gneiss and hornblende er trap rocks.

TOURMALINE .- Hardness, 7; brown, black, red; lustre, glassy ; brittle; form, long, three-sided, striated crystals; breaks irregularly ; composition, silica, lime, magnesium, iron ; common in all south and western part of the county ; often resembles hornblende, but usually in long, fine, radiating crystals.

MICA .- Hardness, 2; whitish; lustre, pearly; elastie; form, in plates and senles ; splits into thin leaves; composition, silica, potas- sium, al. fe .; common in south and western part of county; many varieties, but all are in thin plates, elastic, and not greasy.

FELDSPANS .- Hardness, 6; white, all colors; lustre, glassy, pearly ; brittle; form, usually massive; splits readily in plates; comoposition, silica,. potassium, al .; found in gneiss rocks, and south and western part of county; many varieties; the light-colored constituent of our gneiss rocks.

ASBESTOS .- Hardness, I-4; white, gray ; lustre, dull, silky ; tough ; form, in fibres, like linen or wood; splits into fibres; composition, silica, magnesia, lime, etc .; commen with serpentine; its fibrous nature marks it. A mineral of inereasing value.

GARNET .- Hardness, 7; all colors; lustre, glassy, resinous; brittle; form, round crystals, dodeenhedrons; breaks uneven; composition, silica, fe. en. Ian .; common in gneiss and miea schist; always in crystals, which are never elongated.

CYANITE .- Hardness, 4-7; blue, green, white, yellow ; lustre, glassy, pearly ; tough ; form, in long, flat blades; splits readily one way ; composition, silica, alumina, fe .; found in south and western part of county; its long-bladed crystals and bright blue colors distinguish it.

TREMOLITE .- Hardness, 6; gray, green, white; Justre, glassy ; brittle; form, massive, fibrous; splits irregularly ; composition, siliea, lime, magnesia; found in southern part of county ; bladed or fibrous crystals, gray or white color.

ACTINOLITE .- Hardness, 5-6; bright green ; lustre, glassy ; brittle ; form, crystals, columnar, fibrous ; smooth and even; composition, siliea, magnesia, lime, fe .; found in southern part of county; bladed or acicular crystals, and bright green or yellow colors.

MAGNESITE .- Hardness, 4-5; white, yellow; lustre, glassy, dull; seetile; form, crystals, grnnular, massive; even, smooth ; composition, magnesia, carbonic acid; common in serpentine quarries; radiated erystals on serpentine; foams in aeids.

APATITE .- Hardness, 5; green, all colors; lustre, glassy, all colors; brittle; form, erystals, massive; even, good; composition, phosphate of lime; found in limestone in the southern part of county; in abundance, this mineral would be very valuable for its phosphoric aeid.

GRAPHITE .- Hardness, I; iron-black; lustre, metallie; sectile ; form, seales, massive; into seales; composition, pure carbon; found in gneiss in Uwehlan, Charlestown, Pikeland; scils white paper; is infusible; a valuable mineral.

ConUNDUM .- Hardness, 9; blue, gray, brown; lustre, glassy ; tough ; form, erystals, massive; good in erystals; composition, pure alumnina; found in granular albite in Newlin ; next to the diamond in hardness; very valuable.

EPIDOTE .- Hardness, 6-7; green, yellow; lustre, glassy ; brittle; form, erystals, massive; even, good ; composition, silica, lime, fe. mn .; usually on bornblende in eentral parts of county ; distinguished by its peculiar yellow-green color.

ARAGONITE .- Hardness, 4; white, yellow, red ; lustre, glassy; brit- tle; form, crystals, massive; even, good; composition, carbonate of lime; found in mines and quarries throughout county; same as caleite, but harder, in six-sided crystals; effervesces in abids.

· SCAPOLITE .- Hardness, 5-6; gray, all light colors; lustre, greasy, glassy ; tough ; form, erystals, massive; even in crystals; composi- tion, silica, alumina, lime; found in New Garden, Kennet, Marl- borough; heavier, and more fusible than feldspars; with acids gela- tinizes.

JEFFERISITE .- Hardness, I-5; brown, yellow ; lustre, pearly ; brit- tle; form, plates and scales; into thin plates; composition, siliea, al. fe. mg. water; found with serpentine in Westtown and Newlin; swells up in flame. Called after William W. Jefferis, of West Ches- ter, Pa.

DEWEYLITE .- Hardness, 2-5; yellow, brown; lustre, resinous ; brittle; form, massive, granular; into curved grains; composition, silien, magnesia, water; found with serpentine in West Goshen and West Nottingham ; known by its peculiar resinous appearance.

FLUORITE .- Hardness, 4; purple, wbite; lustre, glassy ; brittle ;

439

THE ZOOLOGY OF CHESTER COUNTY.

form, crystals, massive; even, regular; composition, fluoride of lime; found in Phoenixville, Newlin, and Tredyffrin ; commonly of a beau- tiful purple color, and on limestone or culiate.

BERYL,-Hardness, 7-8; green ; lustre, glassy ; brittle; form, in hexagonal crystals and massive; breaks unevenly; composition, silica, glucinum, aluminium ; found in Newlin, East Nottingham, Westtown; color and hexagonal crystals distinguish it. Contains glucinum.

STAUROLITE .- Hardness, 7-8 ; brown, black ; lustre, glassy ; brittle; form, in crystals which are never slender; uneven; composition, silica, lime, aluminium, iron ; found in West Bradford, West Goshen, West Marlborough ; name from crystals, which are often cross-shaped, never slender.

ZOISITE .- Hardness, 6-7 ; green, gray ; lustre, glassy, pearly ; brit- tle; form, in long, fluted crystals; splits smoothly ; composition, silica, iron, lime, alumina ; found on hornblende rocks, near West Chester and Kennet; green color and crystals fluted, longitudinally marked.

ZIRICON .- Hardness, 7-8; all colors except black ; lustre, adaman- tine; brittle; form, crystals and grains; curved fracture; composition, silica and zirconia; found in South Coventry, West Pikeland, East Bradford, Unionville; lustre, adamantine; hyacinthe, a variety of zoisite.

KAOLIN,-Hardness, 1; white; lustre, dull; sectile; form, massive; even, earthy ; composition, silica, alumina, water; found in Newlin and East Nottingham, Kennet; furmed by the decomposition of gneiss and feldspar ; valuable.

MARGARITE .- Hardness, 4-5; white, gray ; lustre, pearly ; seatile; form, plates, scales ; splits into thin scales ; composition, silica, alu- mina, iron ; found in Newlin, with corundum ; a micaceous-like min- eral, pearly lustre, implanted on corundum.

CHESTERLITE .- Hardness, 5-6; white, yellowish ; Justre, glassy, pearly ; brittle; form, crystals, very perfect ; even, good ; composition, alumina, silica; found in poor-house quarry and Baily's, East Marl- boruugh ; named from Chester County.

ORES. IRON.

PYRITES .- Hardness, 6-7; pale brass-yellow ; strcak, black ; brittle; form, in cubes, crystals, massive; breaks irregularly ; composition, iron and sulphur; common in most parts of county ; yellow celor and striking fire with knife mark it.

LIMONITE .- Hardness, 2-6; brown, yellow; streak, yellow, yellow- ish-brown; brittle; form, massive, columnar; fracture curved; com- position, iron, oxygen, and water; this is our common iron ore; brown or yellow color and yellow streak mark it.

HEMATITE .- Hardness, 6-7; gray, black, red ; strcak, red ; brittle; form, massive, in scales; irregular ; composition, iron und oxygen; found in Warwick, Phoenixville, East Brandywine; not common ; bright, shining pieces, or in scales occasionally.

MAGNETITE .- Hardness, 5-6; iron-black; streak, black; brittle; form, crystals (octahedrons), massive; irregular; composition, iron and oxygen ; found in Warwick, Newlin, Westtown; rare, most valu- able of the ores of iron.

CHAOMITE .-- Hardness, 6; iron-black ; streak, dark brown; tough ; form, massive; irregular, uneven ; composition, iron and chromium ; found with serpentine throughout the county ; often magnetic, on fresh edge, dull lustre.

TITANIC IRON .- Hardness, 6; iron-black ; streak, black to red; brittle; form, massive usually ; uneven, irregular ; composition, iron and titanium; found in Elk, Newlin, Westtown, Thornbury, East Bradford; often magnetic, infusible, contains rare element titanium.

LEAD.

GALENA .- Hardness, 3; lead-gray, blue; streak, gray-black; brit- tle; form, cubes, massive, granular ; regular, sinooth ; composition, lead and sulphur; found at the mines near Phoenixville; its cubical form and soltness mark it.

PYROMORPHITE .- Hardness, 4; green, brown, yellow, wbite; streak, gray to white; brittle; form, culumnar crystals; regular; composi- Lion, lead and phosphorus; found at the lead-mines near Phoenixville; beautiful green columnar crystals; change form on heating.

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History of Chester County, Pennsylvania, with genealogical and biographical sketches, Part 121

Author: Futhey, John Smith, 1820-1888; Cope, Gilbert, 1840-1928 Publication date: 1881 Publisher: Philadelphia, L. H. Everts Number of Pages: 1162

Author: Futhey, John Smith, 1820-1888; Cope, Gilbert, 1840-1928
Publication date: 1881
Publisher: Philadelphia, L. H. Everts
Number of Pages: 1162