Mineral of the Month--April
Potassium Aluminum Silicate
"Delaware Feldspar: Orthoclase"
By Ken Casey
month, we explore in our own backyard: Delaware
Well, we've been around the world on our quest for noble Fluorite. Yes, it's time to
home. So, let's find out what's in our own backyard! Everyone, everywhere,
please join us!
Welcome back to
our newest installment of Mineral-of-the-Month!
Spring is here!
It's now time to begin our outdoor fieldtrip season in Delaware.
We'll not venture far from our clubhouse
this day. A short club bus trip is in order.
So, grab you backpacks. We'll have a picnic lunch and nature hike in Newark, then
return to our clubhouse in Wilmington. Enjoy!
|Path to bridge over the
White Clay Creek
||Entrance to White Clay Creek
Well, Delaware Feldspar is one of
the easier state minerals to understand and to find in
outcrops. It is one basic constituent of our piedmont pegmatites, and more.
Members of the
Plagioclase Albite-Anorthite Group occur in and around Wilmington; whereas among geologic
settings all throughout western New Castle County, Orthoclase predominates. Other
minerals include: Muscovite, Garnet, Beryl, and Quartz.
Yes, even our state mineral
Sillimanite can occur with Potassium or "K-feldspar".
And, there are several varieties to cover. From
microscopic labradorite in Iron and Chestnut
Hills gabbros to Rockford Park gneiss and the large, coarse white feldspar of Woodlawn's
pegmatites, there is so much feldspar choices to visit in Delaware, that more than one
would be required to discuss them all! Therefore, we will visit one type in this
installment, Orthoclase feldspar, and leave the others for future essays.
It's bright orange appeals to the eye, and can be easily seen in stream boulders at White
Clay Creek State Park, for example. This rich potassium feldspar also appealed to
crafters and local manufacturers earlier in Delaware and nearby Pennsylvania's clay
pottery and ceramics industries. More on that later.
Stream boulders of feldspar in the White Clay Creek
Video by Ken Casey
What's in a name?
The word "feldspar" derives from the German word for
"fieldstone". Farmers would clear
these stones from their fields upon tilling the soil in preparation for plowing. It
is a common
usage for any rock found there, regardless of its origin or chemical composition.
Mineralogically speaking, most feldspar, being a common rock
anyway, was found to have
a set of common properties, being either rich in either potassium (K) or Sodium (Na)--and
proportion in between. Orthoclase, or Potassium feldspar's name comes from the Greek
"orthos" and "kalo", meaning "right" and "I
cleave". The name describes K-feldspar's good
cleavage at right angles.
The IMA grandfathered the name before 1959.
So, on today's fieldtrip, we will discover rocks bearing the
Potassium end of spectrum in the
fields of Newark, Delaware.
|View of field and creek
||Lots of feldspar weathered
rocks in the creekbed
Chemistry & Science
Now that we know we've heard the early usage of the term,
let's define what modern
geology defines as a feldspar.
Containing potassium, orthoclase
is an alkali feldspar. It can be found in granites, felsics,
trachytes, and pegmatites. "Orthoclase is the characteristic potassium feldspar
rocks, occurring both alone and in perthitic intergrowth with albite; it also occurs in
|Orange Orthoclase in
||Feldspar and granite rocks in
|Photos by Ken Casey
Amphibolite contains Amphibole and Feldspar. This rock derives
from our rich volcanic past.
Delaware has orthoclase in its biotite gneiss and in other
According to Delaware Piedmont Geology,
orthoclase is a common constituent here. Also, the
Red Clay Valley contains intrusive granite composed of quartz, orthoclase, plagioclase,
or amphibole in coarse grains.
A favorite source, mindat.org,
states in its database that orthoclase is found among the
gabbros of the defunct Brandywine
(Hubbard) Quarry in Wilmington.
|Close-up of Orthoclase
in granite, WCCSP
||More Orthoclase, WCCSP
And, the Water Resources Agency at the University of Delaware
quotes Plank et al. (2000),
stating that "[w]ithin the [Wissahickon] formation are coarse-grained igneous bodies
pegmatites, composed of mica, feldspar and quartz..."
Generally, feldspar's non-porous texture may be due to slow
growth. Might this affect our local
Potter's clay contains feldspar. Delaware clay is no
different. From Red Clay Creek
to White Clay Creek, and in most streams in between, much of our natural clays in New
Castle County may be used to make pottery. In fact, feldspar and clay have been
for industry for over two centuries, and perhaps into to the paleo-people's dawn for
"Born of a prosperous Quaker family, William Ellis Tucker
[1800-32] began in 1826
his earnest experiments [p. 413] in porcelain making, at the old Waterworks building in
Philadelphia. That year he bought [in brief partnership with one John Bird] a property
near Wilmington, Delaware, that yielded feldspar, and another at 'Mutton Hollow in the
state of New Jersey' that provided kaolin or blue clay. In 1827 his porcelains won a
silver medal at the 4th Franklin Institute exhibition, and in 1828 another, for ware
comparing with 'the best specimens of French China'."
Pottery was first used in Woodland I times by the Delaware
paleo-Indians in areas
such as Augustine Creek and Odessa. Perhaps they crafted their vessels from local
|The clay of
White Clay Creek, WCCSP
||Imagine mining clay
here 150 years ago
by Ken Casey
In more modern times, red
orthoclase was crushed and incorporated into ceramic
formulae. Some of this feldspar weathered to high-quality clay. Dr. William J.
Professor of Oceanography and Geological Sciences of the University of Delaware,
Lewes, has published work on the weathering process of feldspar, sometimes into clay.
For example, local feldspathic, coarse-grained granites
decompose in Kaolin clay:
The celebrated deposits around Hockessin are of this character. Dixon s
near Wilmington has produced very fine yields of feldspar. A very notable vein cuts
across the road leading up the Brandywine, about one and a half miles from the
head of the State. Its width is about twenty feet, and the material a mixture of red
orthoclase albite, blue quartz and muscovite. The rock is quarried for the valuable
feldspar, used in the manufacture of artificial teeth....
into Clay at WCCSP
||Ground red clay ready for
|Photo by Ken Casey
||Photo Courtesy of TVE.org
In nearby Delaware County,
Pennsylvania, "[e]xtensive mines of kaolin are worked
at the West End of the county, and an outcrop of pure feldspar rock in Concord
Township is exploited for use of dentists. (See numerous heliotype views of the Kaolin
mines in Report C5.)
I am not sure if clay is mined today in these areas; however,
with special permission,
maybe, one could sample these clays as specimens, or take to use in a ceramics project.
Just about every mineral has a metaphysical use these
days--most of which are positively
employed in healing.
According to the folks at the Foundation for Balance and Harmony, orthoclase
has a good
"Metaphysically, Orthoclase Feldspar has a pleasant, refined energy. Orthoclase
can help overcome tragedy, as well as aligning the chakras and meridians of the physical
body. Known as the "stone of cooperative effort," Orthoclase Feldspar
cooperation among individuals and offers insight into group experiences. Orthoclase
Feldspar can help one find new and unconventional ways to obtain goals, and is said to
foster connection to the wisdom of ancient Egypt."
Since the geology of Newark, Delaware consists of surficial
stream deposits of salmon
orthoclase and its resultant clays, perhaps the good vibes experienced on the University
Delaware campus are due to the happy influence of this colorful feldspar.
As basis of my informal theory are the studies of Earth's magnetic fields. Some
scientists have hypothesized that the associated strong fields hovering over iron deposits
do influence societal behavior at large. For example, many world famous battlefields
have been proven by geophysical surveys to be located over such metallic underscoring as a
temporary weakening in the localized magnetic field occurs.
(Source: Professor Phil Callahan,
|3-D Model of Earth's
(Graphic Courtesy of NPACI)
I would suggest that
locally, the conflict at Old Cooch's Bridge
(September 3, 1777) in
Newark foots the bill. In addition, other area Revolutionary War battlefields, like
of the Brandywine at Chadd's Ford, Pennsylvania (September 11, 1777), might serve as a
Though the U. S. Army suffered defeat at both engagements, our Newark fight is cited as
the first time we flew the Stars & Stripes into battle. Our impetus to fight for
freedom grew greater from there.
Stars & Stripes" Flag, adopted by
Congress on June 14, 1777
(Graphic courtesy of American Flag
On the more peaceful side, the modern town of Sedona, Arizona, attracts those who
search for a greater healing energy. Check out Sedona's live red rocks web
cam, and see
how you feel. Some have noted that "Sedona" spelled backwards is "anodes", or a technical
term related to the transmission of magnetic fields and electricity.
|Sedona "Red Rocks
Live" Cam, May 16, 2007
Without scientific evidence,
though, to support this idea, it is still a personal conjecture;
but, I thought I'd give it a mention to get your minds going. Perhaps you'll study
on the focus of "geology and society".
So, remember to keep your senses open to the affects of the
geology and geography. A
might be a clue to a site's aspects.
We'll venture to a couple of nearby states for our museum
selections for this month. First,
we have the Perkins Geology Museum at the
University of Vermont. Admission is free, and a
one week prior reservation is required. It's accessible when the University is in
you go, why not visit their online Digital Archive for photos of
specimens from their collections.
Second, the Emerald
Village & North Carolina Mining Museum of Little Switzerland, North
Carolina is more than just an old feldspar mine. It is open for individual, family,
and group tours,
and has opportunity to visit three old mines, a museum, gift shop, and to pan for gems!
Either as stone for
walls, pottery, ceramics, and dentition, or as a specimen or healing
stone, or as brick, this versatile, common mineral and clay can serve, even as much as the
enjoyment we derive from the beautiful park landscaping that we've seen today.
Center junior digs for feldspar and other Delaware Treasures
White Clay Creek State Park
Resources by Thomas E. Pickett, 1970
Society "State of the Watersheds"
Chuck Bryant's White Clay
Creek State Park Runner's Page
from the North Carolina Geological Survey
"Feldspar Group" at mindat.org
"Delaware, USA Minerals List at
Here is where DMS Members can add their Delaware
Feldspar photos to share with us.
Orthoclase Feldspar crystals from northern Wilmington, Delaware area
by Ken Casey
Until Next Time
We hope you have enjoyed our historic visit to Delaware
Feldspar. Please join
us next month, for another article, and we shall journey together!
Until then, stay safe, and happy collecting.
I would like to gratefully acknowledge the generous contributions of our fellow
feldspar 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
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
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,
graphics. Use of all other credited materials requires permission of each
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
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.
Feldspar Minerals: Volume 2: Chemical and Textural
by Joseph V. Smith
Feldspar Minerals: Crystal Structures, Physical, Chemical and
Microtextural Properties by Joseph V. Smith and William L. Brown
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: firstname.lastname@example.org.
Invitation to Members
Want to see your name in print? Want to co-author, contribute,
or author a whole Mineral of the Month
article? Well, this the forum for you!
And Members, if you have pictures, or a story you would like to
share, please feel free to offer. We'd like to post them for our mutual enjoyment.
Of course, you get full photo and author credit, and a chance to reach other
collectors, hobbyists, and scientists. We only ask that you check your facts, give
credit where it is due, keep it wholesome for our Junior Members watching, and keep on
topic regarding rockhounding.
You don't even have to be experienced in making a webpage. We
can work together to publish your story. A handwritten short story with a Polaroid
will do. If you do fancier, a text document with a digital photo will suit, as well.
Sharing is the groundwork from which we can get your story out there.
Our club's webpages can reach any person
surfing the net in the world, and even on the International Space Station, if they have a
mind to view our website!
We are hoping for a possible tie-in to other
informative programs upon which our fellow members might want to collaborate.
Contact any officer or board member with your suggestions.
Our next MOTM will
be a surprise. For 2007, we are waiting for your
suggestions. What minerals do you
want to know more about?
Most of the Mineral of the Month
selections have come from most recent club fieldtrips and March Show Themes, and from
inspriring world locales. thus far. If you have a suggestion for a future Mineral of the Month, please e-mail me
at: email@example.com, or tell me at our next meeting.
the Fossil Exposures in the Chesapeake Bay Area" presented by Dr. Lauck
General Club Meeting:
We are meeting at
*Show Committee Meeting, April or May, 2013
*New Home/Lapidary Committee, 2013
*Board Meeting, April, 2013
Next Field Trips
DMS March Show
March 1-2, 2014 at DelTech Stanton
Our 2013 Show
Theme was: "All
That Glitters is as Good as Gold!"
March Show 2013
also commemorates our 50th Show!
It's shiny, yellow, and
is a symbol of 50 Years!Can you guess?
Brook Crick Goethite" by Joe Dunleavy