Delaware mineralogical society

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

 

Middleburg Quarry, Middleburg, PA

Saturday, September 30, 2017: 9:00am meetup

Check your email for final details.

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Delaware Mineralogical Society Field Trip
Middleburg Quarry
October 8, 9:50 am

3499 Quarry Road Middleburg, Pa 17842

On Saturday, May 13th meet up at 0830-9 am at the National Limestone Quarry #1 at 3499 Quarry Rd, Middleburg, PA 17842. We will collect in this large quarry until 12 noon, then break for lunch and head to National Limestone Quarry #2 at 217 Quarry Rd., Mount Pleasant Mills, PA 17853. The two sites are about 5 miles apart and easy to find. We will collect at the Mount Pleasant Mills quarry #2 until 4 pm with the GLMSMC.

These are great collecting sites for calcite, strontianite, celestite, fluorite, wavellite, quartz, cacoxenite, and strengite. These last two only occur as microminerals so bring a hand magnifier. The Mount Pleasant Mills No. 2 quarry also host a good selection of Devonian age marine fossils: brachiopods, gastropods, & trilobites.
Full Safety gear is required for everyone (hard hat, safety glasses, safety boots, long pants, safety vest.)

Children over 10 years old, with full safety gear (helmet, long pants, steel-toed boots, and eye protection) and accompanied by a parent are permitted.
See attached rules and bring a signed, dated waiver when you show up at 0830.
RSVP to me (Tom) by 9pm on Thursday, May 11, 2017.

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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 formation.

Mineral List
Calcite
var: Travertine
ⓘ Fluorite
ⓘ Pyrite
ⓘ Quartz
ⓘ Sphalerite

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 tjpankratz@verizon.net 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.

REQUIRED EQUIPMENT

    HARD HATS, STEEL TOED OR LEATHER BOOTS, SAFETY GLASSES

OTHER EQUIPMENT

    GLOVES

    SLEDGE HAMMERS, CRACK HAMMERS

    WEDGES/ CHISELS

    BUCKET/BOXES/WRAPPING

Middleburg Quarry
Field Trip Report
Delaware Mineralogical Society
By T.J. Pankratz, VP Fields Trips


INTRODUCTION

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 pit.

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:

MINERALS

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 significant finds.

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.

FOSSILS

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 seeds.