Delaware mineralogical society

A Delaware 501(c)(3) non-profit earth-science educational organization

 

Burkholder Quarry

Burkholder Quarry is an active limestone quarry in Ephrata, Lancaster County, PA.

We have found crystals of Calcite, Dolomite, and purple Fluorite, as well as Pyrite.

Burkholder has produced some nice calcite and fluorite crystals.

This is hardrock collecting, so hardhat and safety gear are required. Bring heavy hammers and related tools, as well as water and snacks.

Geology

The Burkholder quarry is located at the northern boundary of the Lancaster Valley Section of the Piedmont Physiographic Province. The Lancaster Valley consists of Cambrian- and Ordovician-aged limestone and dolomites of varying thickness that have been faulted and folded. Immediately bounding the quarry to the north are Triassic-aged red beds, composed of conglomerates, sandstones and shales, some of which are exposed along Denver Road.

The two rock units that are exposed in the quarry are the Lower to Middle Ordovician aged (485 million year old) Epler Formation and the Middle Cambrian (520 million year old) Buffalo Springs Formation.

Geologic Time Scale

The Epler Formation consists of dark gray to black, very finely crystalline, interbedded limestone and dolomite, which is exposed in the northern 4/5 of the quarry. The Buffalo Springs Formation, which is exposed only in the previously mined cove along the southern highwall, is a light to dark gray, fine to medium crystalline, laminated and interbedded limestone and dolomite.

The rocks at Burkholder Quarry were intensely deformed from faulting and folding. A high thrust fault (dipping approximately 70 degrees south), with a displacement of a few thousand, separates the Buffalo Springs Formation in the southern part of the quarry from the Epler Formation in the north. The rocks in the Epler Formation are not as intensely deformed as those in the Buffalo Springs Formation. However, the Epler Formation is steeply dipping at the fault, is cut by several faults with resultant fold development and dips approximately 15 to 20 degrees at the northern highwall.


Mineralogy

Mineralization occurs in veins and in vug fillings in brecciated rock and includes:

Barite, which is rarely found as yellowish plates (5mm);

Calcite, which commonly occurs as massive white veins and scalenohedral crystals and smaller colorless crystals;

Chalcopyrite, which occasionally occurs as golden crystals on and in the calcite;

Dolomite, which occurs as well formed, pink curved crystals usually associated with calcite and fluorite;

Fluorite, which occurs as 3-4mm purple cubes or seen as purple sheen on fractures and joints;

Malachite, which appears as a green halo around chalcopyrite;

Pyrite, which is common as tiny pyritohedron forms associated with calcite and fluorite and as ¼ inch cubes in the green mudstone/limestone layer;

Quartz, which occurs as opaque masses in calcite and occasionally as terminated clear crystals; and

Sphalerite, which is uncommon but sometimes occurs as red-orange masses associated with calcite and dolomite.