Preface
Hello again,
friends! This month, our
Mineral-of-the-Month
takes us back up to Woodlawn
Quarry in historic Delaware and to one railroad stop.
This trip will be a brief one, though, as
our state has only two known locations for Beryl. Our
local weather forecast shows sun with a chill in the air, so bundle up,
and
Let's go!
Introduction
What do we know about Delaware Beryl?
Well, it is a rarity found in our northwestern New
Castle County piedmont granite. Not really mined in Delaware for
it’s beryllium, it was cast aside,
or ground down with it’s host feldspar for use in porcelain and
ceramics.
Most beryl has been found at the historic
Woodlawn Quarry in Wilmington, Delaware. The
variety here is aquamarine--though not of gem quality. Usually, it
occurs a blebs in the granite,
and sometimes as poorly-formed hexagonal crystals. Some light
green subhedral crystals do
also occur.
Just to the north of this locale is the
Pennsylvania beryl found as nice, sometimes gemmy,
crystals in Chester and Delaware Counties. Perhaps there are some
gemstones hiding deep
below the ground in Delaware, yet to be found. As most land is
private, and mining prohibited,
only road construction might reveal a future source. Will they
build a superhighway in rural north
Wilmington west of Route 202? Maybe our great-grandchildren might
tell us, if urban expansion
continues. Though, conservation is most likely the outcome late
into the 21st century.
So come on along, and let’s enjoy a brief virtual
fieldtrip--Enjoy!
Why Delaware Beryl?
Why not?
I asked my fellow club members at our October 8, 2007 general meeting
whether they wanted to know more about Delaware Beryl or Delaware Mica
first. Guess
which one they picked? Please do join us!
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So,
grab your walking
sticks, and let's hike!
Delaware Beryl
locale, Woodlawn
Quarry Trail, Wilmington, Delaware
(Photo by Ken Casey) |
What's in a name?
"Beryl" is
derived from the ancient Greek word "beryllos", meaning "the precious
blue
green color of sea water" stone. Later, the term was
applied to only beryls. The term is so
ancient, that the IMA deems it "prehistoric" in origin.
(Source:
http://en.wikipedia.org/wiki/Beryl)
We have multiple varieties of beryl found around the
globe, including emerald, morganite,
bixbite, goshenite, heliodor, and aquamarine. Delaware's
"aquamarine" is a literal Greek
translation for "seawater".
We can find many varieties of beryl in the world.
We can even make synthetic beryl.
Beryl in The
First State is all-natural, though. Delaware's beryl is
Aquamarine. Beryl
is a
beryllium-rich
cyclosilicate or tectosilicate of chemical formula Be3Al2Si6O18.
On the
Moh’s Hardness Scale, it
ranges from 7.5-8.
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It's tightly-bonded circular molecular structure and
outward hexagonal shape make it an ideal candidate for surviving
as crystals over the eons for us to enjoy. We may find sizes
from near microscopic to several feet long. The Great State of
Maine boasts the larger of the two sizes; whereas, Delaware's
can range from about 1-3 inches in length at best.
Some of the gemmiest aquamarine comes from Brazil; whereas,
the largest crystals in the world are found in far
away Madagascar.
Imagine if we had such gargantuan crystals in Delaware? |
Hexagonal
Aqua Crystals
Drawings by Ken Casey |
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Beryl is rare in pegmatites.
Tourmaline is a more common constituent. Beryllium
seems to occur less often in crustal rocks, than does the more
lithium-rich tourmaline. It
is interestng to note that on the
Periodic Table of
Elements, the order of abundance
begins with Hydrogen, Helium, Lithium, then Beryllium. The
sequence tapers down to
the rare-earth elements (REEs).
Prized as a gemstone since time immemorial,
beryl occurs in a vast array of colors:
blue, green, yellow, red, pink, and clear.
Delaware's aquamarine color derives from
Iron (Fe++). The greener variety comes from
mixtures of ferrous (Fe2+) and ferric (Fe3+) Iron as impurities of its
crystal lattice structure.
Yes, even the oxidation state of Iron can affect the degree of color!
True emerald, on the other hand, has it's
green based upon Chromium (Cr+++).
(Source:
Gems and
Gem Materials Course, Jim Banfield, UC Berkeley)
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| Delaware Aquamarine
Beryl in feldspar (Photo by Ken Casey) |
One could lap Delaware Beryl, but its
typical coincoidal fracture of sub-gem quality
material might cause it to chip or shatter when a vibrating abrasive
wheel is applied. I
know from personal experience as a jeweler, that one should avoid
cleaning a faceted
beryl gemstone in an ultrasonic bath; it's brittle nature allows
microfractures surrounding
inclusions to crack the stone, thus ruining one's client's jewelry.
(I actually learned this
lesson in jewelry school first.)
On the other side of the usage spectrum,
metal refiners choose to crunch beryl
crystals to extract our prime source of beryllium. Delaware's
aquamarine is not used for
this purpose.
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| Delaware
Beryl Locale and green beryl in pegmatite
(Photos by Ken Casey) |
Two exposures of
beryl in granite are known to exist New Castle County, Delaware.
One appears at the Woodlawn Quarry, the other occurs along a
railroad cut.
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Around the Mt. Cuba railroad cut of a bygone era, is a vein
of a coarser-grained granite pegmatite in northern Delaware.
This vein is composed of feldspars, quartz, and black mica.
Schorl and light green beryl have been found here in the past.
(Source:
Delaware Piedmont Geology by Margaret O. Plank and
William S. Schenck)
A blue-green beryl area straddles a few miles over the
Delaware-Pennsylvania border. Covering northern New Castle
County in our state to Chester and Delaware Counties in
neighboring PA.
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(Above): Generalized
Delaware-Pennsylvania Beryl Area Map
Map by Ken Casey ©2007 |
Let's visit the Woodlawn
Quarry locale.
Follow me. I’ll guide us with our favorite
DGS's
GeoAdventure directions.
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We'll cross Ramsey
Run and climb
a curving trail uphill, until we reach the
first right turn. All around us, we can
see eroded century-old mine tailings
strewn about the forest.
Once a thriving quarry, it is now a
protected wildlife sanctuary, run by
the Woodlawn Trustees, whose
permission we need to hike here.
It's a good thing we brought our
walking sticks, and wore our hiking
boots, as safety is important on any
fieldtrip.
Now we can circle round to an
unpretentious mud hole--but wait!
It's not just a water-logged ditch,
it's an abandoned quarry gone to
nature. Let's get a closer look! |
| Eroded tailings trail
through the forest (Ken Casey) |
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When I first came upon this site, this author was
searching for a big hole in the
ground, or even a broken wall or ridge that seemed uplifted from the
forest floor.
But, no. What is here is a smaller scale mine than what I had
expected.
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Water-filled quarry pit at ledge |
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Mica on
ledge soil is slippery--step back, please. |
| (Photos by Ken
Casey) |
Slightly disappointed at first, I realized that
several decades of disuse
left nature to bring back a succession forest. Some trees that
span the site
are large, and nearly a century old! Mammoth maples, oaks, and poplars
have
rooted themselves in quartz, beryl, and feldspar tailings!
It is this dangerously steep and muddy hole that
remains. It marks the center
of activity here. Let's back away from the slippery micaceous
ledge, and have a
closer look at our desired beryl.
Massive beryl can be mistaken for quartz, as pale green or blue blebs
in our quartz
matrix. The color-corrected digital photo below shows the contrast
between the grains
of clear and smoky quartz and the more colorful beryllium aluminum
silicate.
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| Blue-green blebs of aquamarine beryl in
graphic granite (Photo by Ken Casey) |
It seems the fall line geology, as it sits between the Piedmont and the
Coastal Plain, is
similar. Both Delaware and Georgia, for example, have
some granite pegmatites
that contain
blue-green beryls. In fact, all along this boundary,
we can find instances of
beryl geology.
(Source:
Geology of Georgia by Darlene Cooper, Columbus State University)
During the Taconic Orogeny (about 270 mya), scientists believe
that granitic plutons
creating beryl crystals, as the Earth's crust moved on its way to
continental collision.
(Source:
USGS "America's Volcanic Past")
This is how the Mt. Cuba vein most likely formed.
One good way that we could visit
the beryl here is by taking a ride on the
Wilmington & Western Railroad. We'll take the
"club" car. Let's board at Greenbank Station, which happens to be
across the street
from our clubhouse at Greenbank
Mill.
As the train stops at the Mt. Cuba Picnic Grove
area, we'll detrain. After a tasty lunch,
we will walk over to the geology, and have a look. I didn't get
any pictures last trip, so you'll
have to whip out your camera. Maybe you can share them with us.
On our return trip, let's look at some photos of
Delaware Beryl. After that, why not
check out the links and museums below.
Beryl
Aquamarine
University of Delaware Beryl virtual tour
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Color-corrected photos of green
and blue beryl in matrix from Delaware
(Photos by Ken Casey) |
This month's museums are the Virginia Museum of
Natural History and the Paul R. Stewart
Museum. Both house and display area mineral collections.
And, each are located in nearby
Virginia and Pennsylvania, respectively.
The VMNH,
located in Martinsville, hosts approximately 5,000 pieces and 70,000 drill cores.
How many of these are beryl, I do not know. You may have to just
visit them, and explore the
vast collection on your day off. They are associated with the
Smithsonian Institution, and do
offer some nice mineral and fossil
Field Trip Adventures. Yes, yet another fun activity to check
out, after you finish our virtual fieldtrip today!
The
Paul R. Stewart
Museum is located on the campus of
Waynesburg University aptly in
Waynesburg, PA. The university staff have opened their museum to
the public, with the best
access during the academic year.
The PRSM offers collections
to view of early pottery, fossils, and minerals. Check out
their
sample online specimens. It's best to check their website or
call before visiting.
Delaware beryl has only an interest to collectors
and those of us who enjoy the study of
our local geology.
Scientists study it, though it is a rarity in our area. Perhaps
you will find a use for our
Delaware Beryl.
Beryl (Aquamarine) (UC Berkeley)
Woodlawn
Quarry: A GeoAdventure in the Delaware Piedmont
http://webmineral.com/data/Beryl.shtml
Delaware Minerals List
at mindat.org
Geologic Time Scale (USGS)
Here is where DMS Members
can add their Delaware Beryl photos to share with us.
Until Next Time
We hope you have enjoyed our historic visit to
Delaware Beryl. Please join
us next month, for another article, and we shall journey together!
Until then, stay
safe, and happy collecting.
Article Contributors
I
would like to gratefully acknowledge the generous contributions of our
fellow Delaware
Garnet enthusiasts, collectors, authors, curators, professionals, and
club members who
made this work possible.
Thanks.
©2007 All contributions to this
article are covered under the copyright protection of this article
and by separate and several copyright protection(s), and are to be used
for the sole purposes of
enjoying this scholarly article. They are used gratefully with
express written permission of the
authors, save for generally-accepted scholarly quotes, short in nature,
deemed legal to reference
with the appropriate citation and credit. Reproduction
of this article must be obtained by express
written permission of the author, Kenneth B. Casey, for his
contributions, authoring, photos, and
graphics. Use of all other credited materials requires permission
of each contributor separately.
Links and general contact information are included in the credits above,
and throughout this article.
The advice offered herein are only suggestions; it is the reader's
charge to use the information
contained herein responsibly. DMS is not responsible for misuse or
accidents caused from this
article. All opinions, theories, proofs, and views expressed within this
article, and in others on this
website, do not necessarily reflect the views of the Delaware
Mineralogical Society.
Suggested Reading:
Delaware Piedmont Geology including a guide to the rocks of
Red Clay Valley
by Margaret O. Plank and William S. Schenck
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About the Author:
Ken is current webmaster of the Delaware
Mineralogical Society.
He has a diploma in Jewelry Repair, Fabrication &
Stonesetting from the Bowman Technical School, Lancaster,
PA, and worked as jeweler.
He has also studied geology at the University of
Delaware.
And, he is currently a member of the Delaware
Mineralogical Society and the Franklin-Ogdensburg
Mineralogical Society. E-mail:
kencasey98@yahoo.com.
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