Delaware Mineralogical Society Field Trip
October 8, 9:50 am
3499 Quarry Road Middleburg, Pa 17842
We have been invited by the NJ Friends of Mineralogy to join
them on a collecting trip at Middleburg Quarry on Saturday,
Oct 8 at 9:50 am.
We are limited to 5 people so it'll be First-Come,
First-Served. Please respond to me if you wish to attend.
Also, on Saturday, October 29, 2016, we have been invited by
another club, the Gem, Lapidary and
Mineral Society of Montgomery County, Maryland , to join them.
We have been invited to collect at National Limestone’s
Middleburg Quarry (this IS NOT the same location as their
Mount Pleasant Mills Quarry of wavellite fame). The
following information was taken from MinDat:
‘This is National Limestone Quarries' main quarry and
processing location. Excellent locality for calcite
crystals, deep purple fluorite in dark gray limestone, or
white massive calcite matrix, minor occurances of pyrite,
minor drusy quartz crystals, and most importantly, golden
and white calcite travertine (flowstone) from a collapsed
cave feature which was uncovered on the north side of the
main pit during the quarrying operations several years ago.
Many stalactites and stalagmites have been found, as well as
rippled and layered flowstone. Perhaps this may be the only
opportunity to collect specimens from this type of cave
I would add pink dolomite to this list. There is also slate
at one end of the quarry. I don’t know if there are fossils
or not. I and 2 other DMS members briefly visited this site
in 2014 and were greatly impressed by the abundance of
travertine speleothems, which are fluorescent and quite
appealing when thin sliced and acid etched.
This field collecting event is solely for members of the
Delaware Mineralogical Society and members of invited clubs.
If you wish to attend, please contact Tom Pankratz (DMS) by
email at firstname.lastname@example.org or phone 302 239 0140. I’ll
get back to you confirming your successful sign-up within a
day or two; if I don’t please re-contact me.
HARD HATS, STEEL TOED OR LEATHER BOOTS, SAFETY GLASSES
SLEDGE HAMMERS, CRACK HAMMERS
Field Trip Report
Delaware Mineralogical Society
By T.J. Pankratz, VP Fields Trips
Middleburg Quarry is National Limestone Quarries main quarry
and processing location. It is located in central
Pensylvanias Ridge and Valley Region and is primarily
limestone of the Keyser Formation, which formed as a shallow
marine environment in the late Silurian to early Devonian
about 400 million years ago.
Middleburg Quarry is known as an excellent locality for
calcite crystals, deep purple fluorite in white calcite
veins, and golden and white calcite travertine (flowstone)
from a collapsed cave system.
We visited the quarry on April 16, 2016. More than 30
members of 3 mineral clubs participated (Delaware
Mineralogical Society, Friends of Mineralogy Southeast Pa,
and Friends of Mineralogy, Northern New Jersey). Many of us
arrived early and had an excellent opportunity to see an
interesting collection of quarry minerals around the office
and an even more impressive array of speleothems (cave
formations) on the berms around the parking area. At 10 we
were greeted by quarry owner Eric Stahl and after a brief
introduction to himself and the quarry, everyone signed in,
and soon Eric led a very long procession of cars through the
yard past piles of processed stone, and down into the main
The quarry is oval shaped running east-west on the long
axis. It’s about 1000’ wide and 2000’long. It’s a dry quarry
and easy to get around in, both with car and on foot. Eric
led us to a central area where we parked and then showed the
group where different materials could be collected. Of
particular interest was a recently blasted area that had not
been collected before (mid-quarry, south side) and the area
where the collapsed cave travertine could be found
(mid-quarry, north side). Soon everyone was on their way
searching for great collectables. Here’s what we found:
Calcite: Many calcite specimens were found;
some in the limestone and some on the travertine.
White veins of ‘solid’ calcite are abundant in both the grey
limestone and in the black calc-shale.
Many pockets of calcite crystals were found in the limestone
and generally the crystals were clear to whitish and in the
¼” range. See attached photos. Some of the crystals were
reported to have an ‘iron’ coating that gave them an
iridescent appearance. The calcite crystal vugs were found
on the upper level, opposite the travertine ledge(ie., on
the south side of the quarry). However, a recent blast in
the south center wall at the mid-level did not produce
Two forms were found on the travertine. Both were ‘dogtooth’
and golden brown. In one form the individual crystals are
about 1/8” and easily visible; in the other form the
individual crystals are almost too small to see , but occur
in mounds or clumps. In some areas they occur separately,
other places ‘side-by-side’. See photos. Also look at the
photo of the ‘travertine wall’. You will see masses of these
crystals at the bottom of the formation. Note: this photo
was taken many years ago.
Dolomite: There were a few reports of pink
dolomite crystals, presumably in limestone veins. No photos
Travertine/Speleothems: Travertine is
abundant in the quarry both on the lower and the next level
up mid quarry on the north side. All of the travertine is a
honey brown and shows interesting growth patterns that vary
in color tone from whitish to reddish. Smaller hand-sized
pieces may be found on the lower level, 3 to 4’ boulders on
the mid-level and gigantic boulders in the north wall.
Most of the accessable rocks were pretty much ‘worked’ over
in that most surface cave features and calcite crystals were
either missing or damaged, though we were able to collect
some nice flowstone and both types of calcite crystals. Cave
formation specimens are hard to find so we are very thankful
for this opportunity and more than happy with what we
collected (though it would be nice if a few of those huge
boulders would ‘tumble’ from the wall. By the way, all of
the travertine is fluorescent; mostly whitish with veins
varying in intensity and with tones of pink to magenta.
Areas of fractured calcite crystals fluoresce white.
I cut several pieces of the travertine in ¼ “ slices and
treated it with muriatic acid to produce attractive shiny,
rippled surfaces with swiss-cheese holes and clearly visible
growth lines. In general, treating the travertine with ca.
25% muriatic acid removes surface bruises, shines the
surfaces and brings out growth lines.
MaryAnn Levan did a bit of sleuthing and found some
literature on the travertine. She wrote: The best resource I
found was the massive volume The Geology of Pennsylvania
(1999, Charles Shultz, ed. Dept of Geo, Slippery Rock
U).This book has many chapters on specific aspects of
economic geology, and the chapter concerning lime deposits
described this limestone (Keyser, late Silurian, early
Devonian, shallow marine) as a calico rock of dark limestone
with white calcite veins and crystals. There is also a
discussion of limestone caves in the Appalachian Mountain
section of the Ridge and Valley Province and how the caves
generally form on the side wall of a valley. At the time the
book was published, there were 10 public caves in PA, and
the one in the type of limestone we visited was Lincoln
Caverns. If you go to their website, you see cave pictures
with speleothems like the ones we were able to collect.
Fluorite: Purple fluorite in the white
calcite veins in a grey-black ‘calc-shale’ is fairly
abundant at the south western corner of the quarry, as well
on the slopes down in the very lowest part of the quarry.
The fluorite ‘crystals’ ranged in size up to ¾ “. Dissolving
the calcite with muriatic acid brings the fluorite into
relief making for more attractive specimens, however the
grey-black ‘calc-shale’ also slowly dissolves so some care
must be taken. See photos.
The Keyser formation is known for fossils and Middleburg
Quarry is no exception. Here’s what was seen and collected.
Tabulate Coral (aka honeycomb coral):
Several specimens of tabulate coral were found both among
the travertine boulders and on the opposite side of the
quarry. In general these are round, dome-like shaped
aggregates of coral tubes (ca.2mm) approximately 8” across.
Microscopic examination of the ends shows a tightly packed
honeybomb structure. A transverse section across the disc
shows columns of tightly-packed coral tubes. The cut faces
take a reasonably good polish which brings the structure out
more clearly and quite attractively. See photos. They may
make pretty good cabs.
Stromatolite: Elise Juers reported finding
strotomatolite bed along the upper portion of the quarry on
the south side opposite the travertine boulders. They are
found in the second pile from the far end up along the steep
wall. Elise further reports a bed of algal stratomatolite
near the back of pile facing the end of the quarry. The
slabs are approximately 5’ across.
Brachiopods, Crinoids & ?: Elise Juers
reported seeing a few brachiopods and crinoids in the
limestone in the travertine bolder area on the north wall.
She also found some sort of elliptical fossil in dark
limestone near the top that have the appearance of mimosa