CODORUS STONE & SUPPLY COMPANY QUARRY - EMIGSVILLE, PA

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FACT SHEET

Physiographic Setting: Piedmont Province - Lowlands Section

Geologic Setting: Cambrian-aged Vintage Formation. This formation is the oldest of a thick sequence of carbonate units. The quarry is situated in one of the thickest portion of the Vintage Formation.  The contact between this unit and the underlying Antietam Formation is along the northern edge of the present quarry.

Rock Types: Alternating layers of gray-to light-gray dolomite with occasional beds of limestone and limestone conglomerate. Calcite seams are present throughout the unit. Small quartz pods have been observed in the light-gray dolomite.

Structure: The strata dips at a gentle angle to the southeast, making up the northern limb of a broad syncline. The dip does differ near fault zones.         


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Please note that many of these are collected as micros.  Bold names are species often found larger than "micros.")

Minerals Idenified: Aurichacite, aragonite, barite, calcite, chalcopyrite, chamosite, dolomite, epsomite, fluorite, galena, goethite, goslarite, greenockite, gypsum, hematite, hemimorphite, hydrozincite, hexahydrite, jarosite, lepidocrocite, malachite, marcasite, mica, palgorskite, pyrite, pyrolusite,  quartz, rutile, serpentine(?), smithsonite and sphalerite


Fluorite crystal from Codorus Quarry.  Photo by Larry Eisenberger.


The following specimens were collected by micro-mounter Larry Eisenberger of Hanover, PA and photographed by Steve Weinberger of Glyndon, MD.  Numbers following name represent magnification power used.

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Aragonite - 35x 

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Fluorite - 20x

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Stalactitic Goethite - 12x

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Limonite pseudomorphed after Chalcopyrite - 45x

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Pyrite - 25x

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Rutile with quartz - 45x


The following specimens were collected and photographed by Saul Krotki of the state of Washington.

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#1

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#2

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#3

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#4

#1 - Calcite crystal, field of view 2.0 cm.

#2 - Dolomite collected by Eileen Tobin, field of view approximately 4.0 mm

#3 - Saddle shaped dolomite.  2" specimen collected by Eileen Tobin.

#4 - Isolated saddle shaped dolomite crystals, field of view 3.0 mm.


     In October, 2001, the quarry began work on creating a 4th level.  In this expansion, a major sulphide vein was encountered.  Minerals thus far identified include sphalerite, pyrite, greenockite, quartz, hemimorphite, barite, calcite and malachite.  Some of the crystals collected are outstanding.  It seems that the calcite formed in pockets measuring about 2 feet x 2 feet x 2 feet.  Most of the pockets thus far found contain a white, sticky calcium clay containing several hundred "floater" calcite crystals.  Found within the "bottom" rock and "cap" rock are calcite crystals measuring up to 5 inches in diameter.  Sphalerite crystals are well formed lying on quartz crystals.  Sphalerite is also found as massive surrounding calcite voids.    Research continues on this occurrence by JGS.

Collecting Policy: Quarry is closed to collecting.  Quarry has now been gated and trespassers will be fined.

Right  - View of new 4th level.  White area is sulfide and calcite "pocket" area.

Expansion: The quarry is expanding toward the east and south with a new fourth level started in the "quarry" excavation.

Geologic Tour of the Quarry:

The quarry is progressing toward the east and is currently about 150 feet deep, with four levels. The crushing plant is located on the south side of the quarry while the dumps occupy the northern and western borders.

As in most quarry operations, as work progressed in one direction, the older portion of the pit is being back-filled.  The entrance ramp to the lower levels of the quarry still exists on the west side.

 

 

Commonly found in carbonate units are sinkholes. Some carbonate units are more prone then other rock formations to form sinkholes and underground features such as caves.  With its chemical composition of more magnesium than carbonate,  the Vintage Formation is not prone for any major cave develop.  These two sinkholes are marking the location of a fault, which allows water to pass down through the bedrock and forming these features.

 

Joints are fractures in the rock where no movement has taken place.  Closely measuring these joints can assist a geologist in determining the direction and amount of stress that occurred on the rock to deform these strata.  This good example of jointing was exposed in a August, 2000 blast along the south wall on Level 3.

 

Where movement has  taken place, geologists known this structure as a fault.  The Lowlands Section contains many faults, making this section of the Piedmont one of the most complex areas in southeastern Pennsylvania.  When a quarry is following certain rock types and a fault will move or displace the strata,  it is up to the geologist to determine which direction the fault runs.   Can you pick out the fault in this picture below.  For a clue,  trace the light-gray dolomite across the picture

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A key indicator to the type of environment the sediment was deposited in are soul marks.  These markings were caused by rather fast-moving water currents circulating along the bottom of the ocean.  One theory on the environment pictures the sediment forming on a continental slope, which from time to time produced localized submarine slides.  Notice the penny lying on the bed as a scale.

 

Sinkholes are common in carbonate rocks.  Because of the chemistry of various limestones and dolomites,  some formations are more prone for sinkhole development (magnesium vs. calcium). Although several cross sections of sinkholes are been uncovered in the quarry, sinkholes are not a common sight underlain by the Vintage Formation.  Here is one exception, as this sink appeared in the field to the south of the quarry near the Codorus Creek.  The sinkhole measures about 8 feet in diameter and is 15-feet deep.  Sinkholes usually appear along joints or fractures in the rock where surface water is allowed to run and slowly  erode the rock away.  In some causes surface collapse is also caused by the failure of a cave roof.

Who says that quarries aren't beautiful in the winter when most people don't visit because of the cold.   This shot was taken at Codorus!


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