quartz and epidote lenses took place. These, too, have been deformed
by crushing and stretching along Bull Run Mountain and the south part
of Catoctin Mountain. From this fact, taken in connection with the
folding of the schistose planes at Point of Rocks, it would appear
that the deformation was not a single continuous effort.
The ratios of schistose deformation in the igneous rocks are as
follows: diabase, with unstable mineral composition and small
mechanical strength, has yielded to an extreme degree; granite, with
stable composition and moderate mechanical strength, has yielded to
the more pronounced compression.
MINERAL AND KINDRED DEPOSITS.
In point of mineral wealth Loudoun ranks with the foremost counties of
the State. Iron, copper, silver, soapstone, asbestos, hydraulic
limestone, barytes, and marble are some of the deposits that have been
developed and worked with a greater or lesser degree of success.
A large bed of compact red oxide of iron lies at the eastern base of
the Catoctin Mountain, on the margin of the Potomac River. Long before
the Civil War a furnace was erected here by Samuel Clapham, Sr., for
the reduction of this ore, and considerable quantities of it were
formerly transported moderate distances to supply other furnaces. The
Clapham furnace continued in operation until all the fuel at hand was
consumed and then went out of blast. Water power was supplied by the
Catoctin Creek, which flows into the river immediately above the
mountain. To obtain this a tunnel was cut through a spur of the
mountain projecting into a bend of the creek. This tunnel, about five
hundred feet long and sixty feet beneath the summit of the hill, was
cut through almost a solid wall of rock, and, at that day, was
considered a great work.
Magnetic iron ore has been found in certain places, and this or a
similar substance has a disturbing effect upon the needle of the
surveyor's compass, rendering surveying extremely difficult where
great accuracy is required. In some instances the needle has been
drawn as much as seven degrees from its true course. This effect is
more or less observable nearly throughout the Catoctin Mountain, and
has been noted elsewhere in the County.
Chromate of iron was long ago discovered along Broad Run, and, about
the same time, a bed of micaceous iron ore on Goose Creek below the
Leesburg turnpike. Copper ore is associated with the last-named
mineral.
In 1860, the output of pig iron in Loudoun was 2,250 tons, and its
value $58,000. Rockbridge was the only Virginia County to exceed these
figures.
In several localities small angular lumps of a yellowish substance,
supposed to contain sulphur, have been found, embedded in rocks. When
subjected to an intense heat, it gives forth a pungent sulphurous
odor.
Small quantities of silver ore are discovered from time to time; but
the leads have never been extensively worked and many of the richest
veins are still untouched.
Deposits of copper in the schists have long excited interest and led
to mining operations. The amount of ore, however, appears not to have
justified any considerable work.
Near the base of the Catoctin Mountain, where it is first approached
by Goose Creek, marble of an excellent quality is found but has been
little worked. Among the varieties at the quarry are included pure
white, white and pink, blue and white, white and green, serpentinized
and chloritic serpentinized marble. These marbles are of great beauty
and susceptible of a good polish. The calcareous bed here is about
fifty feet thick and reaches southward for three miles with increasing
thickness. At its southern end it is not entirely metamorphosed into
marble, but retains its original character of fine blue limestone.
Northward along this range the thickness of the marble constantly
diminishes and rarely exceeds ten feet. Sometimes there are two beds,
sometimes only one. At Taylorstown, just south of the Potomac, the bed
is about three feet thick; on the north side of the Potomac about
four or five feet. Here, as elsewhere, the beds of marble are inclosed
in a bluish green micaceous schist, which has been thoroughly
transformed by mechanical pressure.
In the vicinity of Leesburg and north of that town, and between the
Catoctin Mountain and the Potomac River, the conglomerate limestone or
brecciated marble is found in abundance, associated with red shale. It
is a calcareous rock, apparently formed in part of pebbles cemented
together and, when burned, produces an inferior lime. It is commonly
known as Potomac marble. Of this variegated marble were formed the
beautiful columns in the old Representatives' chamber of the Capitol
at Washington. The soil in which this rock occurs is extremely
productive and valuable.
The exhibition at the World's Fair, at New Orleans, of the following
specimens of Loudoun minerals claimed much interest from visiting
mineraloguists:
1. _Specular Iron Ore_, from near Leesburg, said to be in quantity.
From Professor Fontaine.
2. _Chalcopyrite_, from near Leesburg, said to be a promising vein.
From Professor Fontaine.
The following were contributed by the "Eagle Mining Company," of
Leesburg; F. A. Wise, general manager:
1. _Carbonate of Copper_, from vein 3' wide, developed to 25' deep.
Assays by Oxford Copper Company of New York give 51 per cent of copper
and 27 ounces of silver per ton.
2. _Sulphuret of Copper_, from vein 10" wide, developed to 50' deep.
Assays by Oxford Copper Company of New York give 12-1/2 per cent of
copper.
3. _Iron Ore_, from vein 4' wide and 50' deep. Yields 55 per cent
metallic iron by assay of W. P. Lawver, of U. S. Mint.
4. _Sulphuret of Copper_, from vein developed 50'. Yields 11 per cent
of copper and 1 ounce of silver per ton by assay of W. P. Lawver, U.
S. Mint.
5. _Carbonate of Copper_, red oxide and glance, from vein 3' wide,
developed to 25' deep. Yields 50 per cent metallic copper and 27
ounces silver per ton by assays.
6. _Iron Ore_, from vein 2' to 4' wide, developed 50'. Yield 55 per
cent metallic iron.
7. _Oxide of Copper_, from Carbonate vein, developed 60' on 4' wide
vein; 25' deep.
8. _Sulphuret of Copper_, from vein 8" to 15" wide, developed 50'.
9. _Iron Ore._
10. _Barytes_, heavy spar, vein undeveloped.
11. _Iron Ore_, from 50' level of Eagle Mining Company's shaft.
12. _Marble_, from quarry of "Virginia Marble Company," three miles
east from Middleburg. The deposit has been demonstrated to be of great
extent; the marble has been pronounced of a very superior quality.
Contributed by Major B. P. Noland.
13. _Marble_, from same as above.
14. " " " " "
* * * * *
17. _Copper Ore_, James Pinkham, from Virginia Department of
Agriculture.
In the "_Handbook on the Minerals and Mineral Resources of Virginia_"
prepared by the Virginia Commission to the St. Louis Exposition,
Loudoun is credited with the three comparatively rare minerals given
below. The two first-named occur nowhere else in the State.
"ACTINQLITE: _Calcium-magnesium-iron, Amphibole_,
Ca (Mg Fe)_{3}(Si O{4}){3}.
Specific Gravity, 3-3.2. Hardness, 5-6. Streak, uncolored.... Fine
radiated olive-green crystals are found ... at Taylorstown...."
"TREMOLITE: _A variety of Amphibole. Calcium._
_Magnesium Amphibole._ Ca Mg{2}(Si O{4}){3}.
Specific Gravity, 2.9-3.1. Hardness, 5.6. Long bladed crystals; also
columnar and fibrous. Color, white and grayish. Sometimes nearly
transparent. Found in the greenish talcose rocks at Taylorstown."
_Chromite_, of which no occurrence of economic importance has yet been
discovered in the County or elsewhere in Virginia.
"[9]On the eastern flank of the Catoctin rests a thin belt of mica
slate. This rock is composed of quartz and mica in varying
proportions, and this belt, on reaching the Bull Run Mountain, there
expands itself, and forms the whole base of that mountain, and where
the mica predominates, as it does there, it sometimes forms excellent
flagging stones."
[Footnote 9: Taylor's _Memoir_.]
* * * * *
"Immediately at the western base of the Catoctin Mountain, a range of
magnesian or talcose slates occur traversing its whole length.... In
this range a vein of magnesian limestone is met with, and is exposed
in several places. It however is narrow, in some places only a few
feet in thickness, and being difficult to obtain is not much sought
after for burning."
* * * * *
"Along the eastern side of the valley (Loudoun) gneiss is frequently
met with on the surface, and where the larger streams have worn deep
valleys, it is sometimes exposed in high and precipitous cliffs. This
is more particularly the case along Goose Creek and Beaver Dam.
Associated with it, however, is clay slate, not so much in rock as in
soil, for it being more readily decomposed is seldom found on the
surface, except as soil. These two varieties are often met with side
by side in thin layers, and their combination at the surface forms a
peculiarly favorable soil for agricultural purposes. The gneiss from
the quartz it contains makes a sandy soil, while the clay slate gives
it tenacity. This happy combination is a prevailing feature of this
entire valley, and renders it one of the best farming sections in
Virginia.
"Another rock that is a valuable acquisition is hornblende. This kind
when first taken from the ground, is always covered as with a coat of
rust. This is doubtless the fact, for the oxydasion of the iron it
contains gives it that appearance, and colors the soil a reddish hue
in its immediate vicinity. Wherever this rock abounds, the soil is
durable and the crops are usually heavy. It is sometimes met with
having a fine grain, and so very hard as to be almost brittle, though
generally very difficult to break, and when broken strongly resembling
cast-iron, and will sometimes ring, on being struck, almost as
clearly. It was used very much formerly for making journals to run
mill-gudgeons upon. When found on the surface, it is usually of a
rounded form...."
However, much of the rock of the valley partakes of the nature of both
hornblend and gneiss, and has been aptly termed a "hornblend gneiss
rock."
Beds of magnesian or talcose slate, sometimes containing crystals of
sulphuret of iron, are frequently met with in this section, and at the
base of Black Oak Ridge, which is composed chiefly of chlorite slate
and epidote, another bed of magnesian limestone is found. Containing
about 40 per cent of magnesia, it makes an excellent cement for walls,
but is of little or no value as a fertilizer.
SOILS.[10]
The soils of Loudoun vary greatly in both geological character and
productiveness, every variety from a rich alluvial to an unproductive
clay occurring within her boundaries. In general the soils are deep
and rich and profitably cultivated.
The heavy clay soils of Loudoun are recognized as being the strongest
wheat and grass soils. The more loamy soils are better for corn on
account of the possibility of more thorough cultivation. However, the
lands all have to be fertilized or limed to obtain the best results,
and with this added expense the profit in wheat growing is extremely
uncertain on any but the clay soils. The loamy soils are especially
adapted to corn, stock raising, and dairying, and they are largely
used for these purposes. The mountain sandstone soils, which are rough
and stony, are not adapted to any form of agriculture; but for some
lines of horticulture--as, for instance, the production of grapes,
peaches, apples and chestnuts--or forestry they seem to offer
excellent opportunities. The schist soil of the mountains, although
rough and stony, is productive, easily worked, and especially adapted
to apples, peaches, and potatoes. The shale and mica soils, although
thin and leachy, are especially adapted to grapes, vegetables, and
berries, and other small fruits. These soils should be managed very
carefully to obtain the best results. They are easily worked and very
quickly respond to fertilization and thorough cultivation. It is very
probable that market gardening and fruit raising on these types would
prove profitable. It seems, however, that peach trees are short lived
on these soils. The meadow lands are low and subject to overflow,
although otherwise well drained. They are best adapted to the
production of corn, grass, and vegetables.
[Footnote 10: For the bulk of the information appearing under this
caption the author is indebted to Carter's and Lyman's _Soil Survey of
the Leesburg Area_, published in 1904 by the United States Department
of Agriculture.]
That part of the County lying east of a line drawn from the Potomac
River near Leesburg, by Aldie to the Fauquier line, is much more
unproductive than the western portion, partly on account of an
inferior soil, and partly in consequence of an exhausting system of
cultivation, once so common in eastern Virginia, i. e., cropping with
corn and tobacco without attempting to improve the quality of the
soil. When impoverished, the lands were thrown out to the commons.
Large tracts that formerly produced from thirty to forty bushels of
corn to the acre, still remain out of cultivation, though many of the
present proprietors are turning their attention to the improvement of
these soils and are being richly rewarded.
In this section, particularly along Goose Creek, trap-rock occurs,
sometimes covering large surfaces, at other times partially covered
with indurated shale, formed from the red shale of this region which
has become hardened by the heat of the intruding trap. Where this rock
occurs covering large surfaces, nearly level, "the soil is a dark
brown colored clay, very retentive of moisture and better adapted to
grass than grain.... A deficiency of lime probably occurs here, and
there may be some obnoxious ingredient present. Minute grains of iron
sand are generally interspersed through this rock, and as it is not
acted upon by atmospheric influences, its combination may contain some
acid prejudicial to vegetation. Where this rock is thrown into more
irregular elevations, and is apparently more broken up, the soil is
better."[11]
Near the Broad Run Bridge the soil is deplorably sterile. "In many
places it is but a few inches in thickness, and the rock below, being
compact, prevents the water from penetrating much below the surface,
thus causing an excess of water in rainy weather, and a scarcity of it
in fair weather. The red shale does not appear to decompose readily,
as it is found a short distance beneath the surface, and the strata
dipping at a low angle, prevents the water from freely descending into
this kind of soil."[12]
[Footnote 11: Taylor's _Memoir_.]
[Footnote 12: Ibid.]
There is a huge belt of red land, known as "the red sandstone
formation," extending from the Potomac through a part of each of the
counties of _Loudoun_, Fairfax, Prince William, Fauquier, Culpeper,
and Orange, which, with judicious cultivation, might be rendered
liberally productive. Professor W. B. Rogers, in his report to the
legislature of Virginia, in 1840, described it under the head of the
"secondary formation in the northern district." "The general form of
this area," he wrote, "is that of a prolonged triangle, extending in a
direction from SSW. to NNE., having its apex at the southern
extremity, and gradually expanding until it reaches the Potomac.
Measured at a point on the Potomac between the mouths of Goose Creek
and Broad Run, its length is about 80 miles. Its greatest breadth, as
measured near the Potomac, and parallel to the road leading from
Leesburg to Dranesville, is about 15 miles. This, in round numbers,
gives 600 square miles for the area of this region."
Bottom lands of inexhaustible fertility and rich upland loams are
commonly met with north and south of Leesburg for a considerable
distance on either side of the turnpike leading from Point of Rocks,
Md., at one extremity of the County to Middleburg at the other.
Limestone occurs in vast quantities throughout this zone, and there
are present all the propitious elements that will be enumerated in the
treatment of the soils of other areas.
The land here is in a high state of cultivation and, according to its
peculiarly varying and unalterable adaptability, produces enormous
crops of all the staple grains of the County.
The soil in the vicinity of Oatlands, included in this zone, is stiff
and stony, except such as is adjacent to water courses, or the base of
hills, where it is enriched by liberal supplies of decayed matter,
which render it loamy and inexhaustible. In the main, it is of a
generous quality, so pertinaciously retaining fertilizers as to
withstand the washing of the heaviest rains. Still it is an anomaly
that some of the richest areas in this region will not produce wheat;
while, in the cultivation of rye, oats, and corn, satisfactory results
are almost invariably obtained. Likewise there are but a few parcels
whereon white clover does not grow spontaneously and in the greatest
abundance. Than these, better pasture lands are found nowhere east of
the Blue Ridge. Limestone occurs here in vast quantities.
In the Valley of Loudoun, between the Catoctin and Blue Ridge
mountains, the soil is formed from gneiss, clay-slate, hornblend,
greenstone, and quartz. The happy combination of these materials
produces a most excellent and durable soil, containing, in fair
proportions, alumina, silex, potash, lime, and other fertilizing
minerals. Certain fertilizers have been successfully employed in
improving its natural fertility, and when it is partially exhausted by
excessive tillage, rest alone will restore it.
_Loudoun Sandy Loam._
The Loudoun sandy loam consists of from 8 to 12 inches of a heavy
brown or gray sandy loam, underlain by a heavy yellow or red loam or
clay loam. Often the subsoil contains a considerable quantity of
coarse sand, making the texture much the same as that of the soil. The
sand of the soil and subsoil is composed of very coarse rounded and
subangular quartz particles. The surface material is not a light sandy
loam, but is more like a loam containing considerable quantities of
very coarse quartz fragments. It is generally quite free from stones,
but small areas are occasionally covered with from 5 to 20 per cent of
angular quartz fragments several inches in diameter.
The Loudoun sandy loam occurs in irregular areas of considerable size
in the intermediate valley between the Blue Ridge, Short Hill, and
Catoctin mountains. The largest area of the type is found in the
vicinity of Round Hill.
The topography of this soil in the valley varies from gently rolling
to hilly, the slopes being long and gently undulating, while along the
valley walls and in the uplands it is ridgy. Owing to the position
which this type occupies, surface drainage is good. The light texture
of the soil admits of the easy percolation of water through it, and,
except where the subsoil contains considerable sand, the soil moisture
is well retained. In dry weather, if the ground is cultivated, a mulch
is formed, which prevents the evaporation of the soil moisture and
greatly assists the crops to withstand drought.
Nearly the whole of this type is in cultivation. Where the forest
still stands the growth consists chiefly of oak. The soil is easy to
handle, and can be worked without regard to moisture content. It is
considered a good corn land, but is too light-textured for wheat,
although a considerable acreage is devoted to this crop. Corn yields
at the rate of 40 or 50 bushels per acre, wheat from 12 to 15 bushels
and occasionally more, and grass and clover at the rate of 1 or 2 tons
per acre. The productiveness of the soil depends greatly on the sand
content of the subsoil. If the quantity be large, the soil is porous
and requires considerable rain to produce good yields. If the clay
content predominates, a moderate amount of rain suffices and good
yields are obtained. Apples, pears, and small fruits do well on this
soil.
_Penn Clay._
The Penn clay consists of from 6 to 12 inches of a red or
reddish-brown loam, resting upon a subsoil of heavy red clay. The soil
and subsoil generally have the Indian-red color characteristic of the
Triassic red sandstone from which the soil is in part derived. From 1
to 10 per cent of the soil mass is usually made up of small sandstone
fragments, while throughout the greater part of the type numerous
limestone conglomerate ledges, interbedded with Triassic red
sandstone, come to the surface. In other areas of the type numerous
limestone conglomerate bowlders, often of great size, cover from 10 to
25 per cent of the surface.
This latter phase occurs in the vicinity of the Potomac River near
Point of Rocks, Md., and near the Potomac, 3 miles north of Leesburg,
and in these places the heavier phase of the type occurs, the clay
often being very near the surface. In other parts of the County, where
the limestone conglomerate is not so preponderant, or where it lies
deeper and is mostly unexposed, the surface soil is deeper, often
consisting of 18 inches of loam. The land is locally termed "limestone
land." Near Catoctin Mountain the rocks seem to have weathered to
considerable depth, there being no exposures or outcrops. Here the
soil has been washed away from some of the more elevated small areas,
and the heavy red clay subsoil is exposed.
In a great many places along the base of the mountain the formation of
this type is somewhat complicated by the wash from the mountain, which
consists principally of subangular quartz fragments, from 1 to 4
inches in diameter. This rock sometimes forms as much as 30 or 40 per
cent of the soil mass. This phase is called "gravelly land," and is
hard to cultivate on account of its heavy texture and stony condition,
although it is inherently productive.
This type occurs in one irregular-shaped area, about 15 miles long,
varying from less than 1 mile to 3 or 4 miles in width, being cut by
the Potomac River just east of Point of Rocks, Md. It thus lies in the
central part of the County, in the Piedmont Plateau, extending from
immediately north of Leesburg, and skirting the eastern foot of
Catoctin Mountain.
The general surface drainage is good, there being many small streams
flowing through the type and emptying into the Potomac River. The
stream beds are but little lower than the surface of the surrounding
land, while the slopes are long and gentle. Excessive erosion scarcely
ever occurs. The heavier phase of the type would undoubtedly be
improved by tile draining, as it is usually lower lying than the
lighter phase. The heavier phase bakes and cracks in dry weather much
the same as the heavy limestone soils of the Shenandoah Valley, but
with the lighter phases, where the soil covering is deeper, good tilth
is easily maintained throughout the growing season.
Corn, wheat, clover, and grass are the crops grown, of which the
yields are as follows: Corn, from 40 to 60 bushels per acre; wheat,
from 15 to 25 bushels per acre, and clover and grass, from 1-1/2 to
2-1/2 tons of hay per acre.
The Penn clay is the most highly prized soil of the Piedmont region of
Loudoun and brings the highest prices.
_Penn Stony Loam._
The Penn stony loam consists of from 8 to 12 inches of a red or
grayish heavy loam, somewhat silty, underlain by a heavier red loam.
From 10 to 60 per cent of gray and brown fragments of Triassic
sandstone, ranging from 1 to 6 inches in thickness, cover the surface
of the soil. The color is in general the dark Indian-red of the other
soils derived from Triassic sandstone, being particularly marked in
the subsoil.
This type occurs in the southeastern part of Loudoun, on the Piedmont
Plateau. It occupies three small areas whose total extent probably
does not exceed two and one-half square miles. It is closely
associated with the Penn loam and grades gradually into that type. The
only great difference between the two is the presence of sandstone
fragments in the Penn stony loam.
The topography varies from gently rolling to hilly and ridgy, with
slopes that are sometimes rather steep. However, the surface is not so
broken as to interfere with cultivation, and the slopes are usually
gentle.