DMS_banner12.jpg (71459 bytes)
Home About Us Field Trips March Show Board/Officers Geogram Sample Meetings Members Links

 

 

 

 

 

                           Mineral of the Month--February 2008

                              Exotic Pegmatites, Part 1

                                                   Various and Sundry Minerals & Chemistries

                                                   At least SiO2

 



                                        "Exotic Pegmatites"

                                              By Ken Casey

Preface
Introduction
Why Exotic Pegmatites?
What's in a name?
Chemistry & Science
Some Exotic Pegmatite Geology
Two Museums of Note
Uses
Links
Members' Gallery
Article Contributors
Photo & Graphics Credits
Suggested Reading
Invitation to Members
Past Minerals of the Month


Pegmatite

or a world globe

Image by Ken Casey
2008

   
 

Exotic pegmatites...

 

...!

(Top, left): , Wilmington, Delaware
Photo by Ken Casey 2008

(Top, right):
Photo by Ken Casey 2008

Preface    

    

     Hello, again, fellow adventurers!  This month, our Mineral-of-the-Month takes us all over the
First State to find quartz in all it's forms.  In this two-part series on Delaware Quartz, we'll
venture across all three counties: New Castle, Kent, and Sussex in search of our most popular
silicon mineral.

     Summer is still lingering, but bring your light jacket.  The weather promises to be bright and
sunny today, so
Let's go!

 

Introduction

     

    In part 1, we covered igneous quartz and bedrock, and touched upon our beach sands. This
month, we will study the sands and pebbles of time that lie around Delaware’s coast, rivers,
creeks, and aquifers. In other words, sedimentary quartz.

     Erosion by wind and water has deposited grains of quartz sand from microscopic to larger
pebbles here. Though glaciations did not officially touch Delaware topography, subsequent
erosion of glacial material left to the north of us, from Pennsylvania and New Jersey, did arrive
here eons ago.

     Work by geologists gives us an overview as to the surficial occurrences of tumbled quartzes.
And, digs by both archaeologists and gravel miners point to areas rich in rounded silicon dioxide,
which can help us to paint a picture of the widespread availability of this mineral to view and to
collect.

     As quartz was geologically created in a range of colors, whose original occurrences span the
greater northeastern United States and Canada, the area of colorful material which have aggregated
over Delaware’s ancient landmass is vast. So, that means that we can find colors ranging from clear,
white, yellow, pink, purple, and green strewn across our local landscape.

     Though most terrigenous erosional detritus is from places outside of Delaware, these mineral
morsels do belong here by virtue of having arrived under our feet thousands of years before native
Delawareans came here. Since they are ours to collect (with appropriate permissions, of course),
we can assemble a vast array of colorful specimens to show and to share!

     So come on along, we have another Delaware Quartz fieldtrip to make!

     We can, however, take our pick of geology hikes to view them in situ. Or, as the Delaware
Geological Survey has organized itineraries for us, called GeoAdventures.  We''ll share a bit
from the Survey's suggestions, coupled with our club's and this author's field experience.

     Our article will landscapes.  Enjoy!

 

Why Delaware Quartz?

 

      Our local .  Please do join us!

   

     And, with a simple trail off of the entrance to the parks, such as to our Brandywine Creek State Park, north of Wilmington, we can quickly find specimens to observe.

     So, grab your walking sticks, and let's hike!

 

Easy to find garnet in host rock, BCSP
(Photo by Ken Casey)

 

     

What's in a name?   

 

     Quartz

  (Source: http://en.wikipedia.org/wiki/Quartz)

     
Pomegranate in cross-section   Small garnets in situ from Brandywine Creek State Park
Photo by Peter (Fir0002), wikipedia.org   Photo by Ken Casey

     Much of

 

    Greek

  (Source: http://www.jewelrysupplier.com/2_garnet/garnet_mythology.htm

     The name “quartz” was grandfather prior to 1959 by the IMA.

   

 

 

Chemistry & Science

     Delaware's quartz is a silicate of chemical formula SiO2.  It

     On the Moh’s Hardness Scale, it ranges from 6.5-7.5.

 

Where found?

DELAWARE. Pegmatites?

DIXON'S QUARRY.—Columbite.
NEWARK.—Quartz crystals, doubly terminated, loose in soil.
http://books.google.com/books?id=KAgRAAAAIAAJ&pg=PA504&lpg=PA504&dq=delaware
+and+quartz&source=web&ots=A2bqv9a2Qd&sig=_wEeLUzK-xny2snS2tC0vN5QRRY

         
Garnet sandpaper    60-Grit Garnet sandpaper   Garnet used to make sandpaper 
Photo courtesy of Grimes Industrial    Photo courtesy of Woodzone   Photo by Ken Casey 

   

  Though

  (Source: http://www.uwgb.edu/dutchs/EarthSC102Notes/102ROCKS.HTM

     In the photos below,

         
 Photos of Appalachian mountains and plateaus overlooking Susquehanna River at Red Hill, Hyner, PA  (Photos by Ken Casey)
 

     Delaware has

  (Source:) 

         What .

(Source: )

Garnet-laden drill core samples
(Photo courtesy of Oliver Holm, Geoscience Australia)

     For example,

     Our Piedmont

     Therefore,

           

 

Some Delaware Garnet Geology

     Gneiss is the primary

     
Almandite Garnet crystal Photomicrograph, South Carolina's Appalachian Piedmont    Almandite Garnets the size of dimes in matrix,
Brandywine Creek State Park 
Photomicrograph by Harmon Maher ; Photo by Ken Casey 
 

     The smallest Delaware Geological Survey.
The largest may be perus

   

     Our eastern Piedmont runs northeast-southwest, the entire length of the middle-Atlantic coastal area, intersecting at nine states and the District of Columbia. So, of course, similar garnet occurrences can be found in other states. Our region is marked with outcrops, exposing a modest wealth of garnet viewing areas. We will concentrate on our area’s Wissahickon Formation and Wilmington Complex of rocks.

 

Generalized Piedmont Map; Piedmont is Tan 
(Courtesy of Karl Musser, Cartographer, wikipedia.org

 

 
     According to DGS publication Delaware Piedmont Geology by Margaret O. Plank and William S. Schenck, “”

  (Source:  http://www.udel.edu/dgs/Publications/pubsonline/SP20.pdf
)

 

   

     More sp

  (Source: http://vulcan.wr.usgs.gov/LivingWith/VolcanicPast/Places/volcanic_past_delaware.html)

     A rare igneous garnet is found in the pegmatite of the Woodlawn Quarry.  The locale may be found
in the red area of the Generalized Geologic Map of Delaware, below.

    Why not try this one: Woodlawn Quarry: A GeoAdventure in the Delaware Piedmont

 
                   Generalized Geologic Map of Delaware, courtesy of the Delaware Geological Survey
                       Prepared by: Nenad Spoljaric and Robert Jordan, Revised by: Thomas E. Pickett

 
Physiographic Map of Pennsylvania, Pennsylvania Geological Survey
 

Microscopic Garnet

 

     Yes, right in o

     
Nearly microscopic garnets at BSP    Close-up of tiny garnets at BSP 
Photos by Ken Casey 
 

     As BSP is adjacent to our clubhouse at Historic Greenbank Mill, and drillin

 

     
 

University of Delaware
Delaware Geological Survey
Open File Report No. 38, June 1995
Data Report on Rock Cores from Red Mill Road, Harmony Road,
Prices Corner, and Newport, Delaware

DGS ID: Cc13-17 SAMPLE NO.: 24896 QUAD: WIS
FIELD NO.: S-8-1 DATE ENTERED: 3/3/93
LOCATION: Prices Corner - core, 66' (58' ASL)
ROCK UNIT: Wilmington Complex ORIENTED SEC.:
STAINED: K-feldspar: Y Plagioclase: Calcite: Cordierite:
LITHOLOGY: Biotite gneiss
MAJOR MINERALS MODE (%) ACCESSORY MINERALS

quartz 38.0 zircon, apatite
plagioclase 38.0 monzanite halos in biotite,
biotite 22.0 colorless to yellow
garnet 1.0
opaques 1.0 RETROGRADE MINERALS
sillimanite mats x
                Pale green mineral with opaques

NUMBER OF POINTS COUNTED: 400
COMMENTS
The rock in this core is a fine-grained dark biotite gneiss with biotite grains aligned vertically.

FABRIC AND TEXTURES

Plagioclase: Equant xenoblastic grains, partial twinning, round inclusions of quartz and plagioclase
Quartz: Undulatory extinction; large subgrain boundaries with lobate edges
Biotite: Pleochroism is light brown to dark brown; laths have a preferred orientation and are aligned to define the foliation
Garnet: Tiny xenoblastic to subidioblastic garnets grow over other grain boundaries; some with small inclusions of opaques; one garnet is elongated in the foliation
Opaques: Irregular shapes; two different opaques; in reflected light, one is dark and the other is silver

 
     
 

    The fabri

  (Source: http://www.udel.edu/dgs/Publications/pubsonline/report38/31.html

 

 

xpl off of 1 edge of Garnet 10* (Almandite crystal thin-section)
(Photomicrograph by UCLA's Petrographic Workshop)
 

     If you like the smalle

 

Macroscopic Garnet

     If,

     As the Delaware Greenways Project expands, we’ll be able to hike directly to other geologic locations
rather efficiently on future MOTM fieldtrips. Thanks to the State of Delaware and its partners, our educational
and recreational experiences will be enhanced.

     Now, to the park-at-hand. Follow me.  I’ll guide us with the DGS's GeoAdventure directions, so that we
may tread lightly, and leave the squirrels and woodpeckers to their business.  Don't worry, we'll see garnets!

    

Rocky Run at BCSP    Boulder field at Rocky Run, BCSP    Close-up of garnets in matrix 
Photos by Ken Casey 
 

     "To see the contact, you need to follow the stream to the confluence of Hurricane Run and Rocky Run
and stay on the northeast side of Rocky Run. (E, Figure 2). The exposed contact is difficult to recognize
and probably interesting only to geology students at the high school or college level. It is exposed in a ten
foot area along the northeast side of Rocky Run where dark, fine grained Wilmington Complex gneisses are
interlayered with light colored Wissahickon gneisses. The Wissahickon rocks appear to have been melted
and recrystallized to form granites with thin layers of garnets. The biotite and sillimanite that occur in the
Wissahickon gneisses are replaced by tiny garnets. This reaction in which garnet replaces biotite and
sillimanite occurs only at very high temperatures. The Wilmington Complex layers vary in thickness between
3 inches and 2 feet, and are dark solid, massive rocks.”

  (Source:  http://www.udel.edu/dgs/Education/bluerocks.html

     Let's zoom in on our gneiss garnets. 

         
Large red garnets in Rocky Run rock, BCSP    Closer view    Closest view 
Photos by Ken Casey 
 

Other Quartz Experiences

     Now that we have sampled views of some of the largest garnets in Delaware, let's have lunch.  I'll trade
you an extra pomegranate for half of your peanut butter and jelly sandwich.  We can discuss other garnet
experiences over dessert, if you like. 
 

     Of course, our club visits collecting sites for garnet all around our area. Please do inquire upon how to
join us as members, and can benefit from our club fieldtrips. Our trips our setup and led by our own Bob Asreen,
Geologist, and Vice-President of Fieldtrips.

 



(Top): Gem Trails cover by Mark Webber








(Right): Close-up of Wissahickon Valley garnets in schist matrix from Fairmount Park
 

     Gem Trails of Pennsylvania and New Jersey by Scott Stepanski and Karenne Snow, suggests that very small, nicely faced, and deep red Almandine garnets may be found weathered out of their host schist at Fairmount Park, Philadelphia. This author visited there about three years ago, and found small quantity on the trail--enough to fill a thimble or two.

     I was fortunate enough to meet Ms. Snow a couple of years ago at one of the Cape-Atlantic Rockhounds events.  She was kind enough to sign my copy of her book.  I think it brought me luck, since I've had some good experiences collecting from locations that she and Scott Stepanski had recommended.

     These Wissahickon Valley garnets may be collected from Fairmount Park in Philadelphia. According to the book, garnets wash out of the surrounding schist, to be collected on the trail. 
Good Luck!

 
 
 

    

     If

    

Two Museums of Note

     Our MOTM format will continue to offer us information on two places we can visit to learn more
about minerals, such as this month's

 

Uses

     As Delaware quartz occurs in commerical quantities as gravel and sand, these easily accessible
forms are readily used in construction and landscaping.  Our large stretches of bay and ocean
beaches are for recreation, and as nature preserves.

 
Exposed garnets from Brandywine Creek State Park, 2004
Perhaps by now, they are eroded out--who knows?
(Photo by Ken Casey)
 
 

Links

 

Pyroxenes (and amphiboles), Tourmaline and Garnet (UC Berkeley)

Woodlawn Quarry: A GeoAdventure in the Delaware Piedmont

http://webmineral.com/data/Almandine.shtm

http://www.rbmason.ca/databank/mineral/garnet.html

Delaware Minerals List at mindat.org

 

Members' Gallery

     Here is where DMS Members can add their Delaware Quartz photos to share with us.

    

     
Almandine on Muscovite, crystal 2.4 cm x 2.0 cm

  Almandine crystal, 2.6 cm x 2.1 cm
     
Almandine on Muscovite, crystal 2.9 x 2.1 cm   Almandine crystal, 1.5 cm x 1.3 cm

 

Until Next Time

     We hope you have enjoyed our historic visit to Delaware Quartz.  Please join
us next month, for another article, and we shall journey together!

    
Until then, stay safe, and happy collecting. hardhat2a.gif (5709 bytes)

 

 

Article Contributors

 

wikipedia.org

Delaware Piedmont Geology by Margaret O. Plank and William S. Schenck, DGS

 

 

Photo & Graphics Credits

    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.

Arthur Koch, DMS Member, B. S. in Geology, Mineral Photographer

Marchex, Inc., World Flag Database

wikipedia.org

Delaware Piedmont Geology by Margaret O. Plank and William S. Schenck, DGS

Nenad Spoljaric and Robert Jordan, Thomas E. Pickett, Delaware Geological Survey

Physiographic Map of Pennsylvania, Pennsylvania Geological Survey

Photomicrograph by UCLA's Petrographic Workshop

Gem Trails cover by Mark Webber



2008 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

Gem Trails of Pennsylvania and New Jersey by Scott Stepanski and Karenne Snow

 

KEN.JPG (31503 bytes)

   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.


Invitation to Members

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 2008, we are waiting for your suggestions.  What minerals do you want to know more about?

aniagate.gif (1920 bytes)

____________________________________

Most of the Mineral of the Month selections have come from most recent club fieldtrips and March Show Themes, and from inspriring world locales, and suggestions by our members, thus far.  If you have a suggestion for a future Mineral of the Month, please e-mail me at: kencasey98@yahoo.com, or tell me at our next meeting.

 

 

Past Minerals of the Month
August 2007 Mineral of the Month: Schorl (Black Tourmaline)
July 2007 Mineral of the Month: Rubellite
June 2007 Mineral of the Month: Elbaite 
May 2007 Mineral of the Month: Delaware Feldspar, Part 2 
April 2007 Mineral of the Month: Delaware Feldspar: Orthoclase
March 2007 Mineral of the Month: "The Colors of Fluorite"
February 2007 Mineral of the Month: Pennsylvania Fluorite
January 2007 Mineral of the Month: Sillimanite
December 2006 Mineral of the Month: Hedenbergite by Karissa Hendershot
November 2006 Mineral of the Month: Brandywine Blue Gneiss
October 2006 Mineral of the Month: Spessartite by Karissa Hendershot
September 2006 Mineral of the Month: Native Silver
August 2006 Mineral of the Month: Kryptonite
July 2006 Mineral of the Month: Azurite
June 2006 Mineral of the Month: Pyromorphite
May 2006 Mineral of the Month: Tsavorite by Karissa Hendershot
April 2006 Mineral of the Month: Variscite
March 2006 Mineral of the Month: Petrified Wood, Part II
February 2006 Mineral of the Month: Petrified Wood, Part I
January 2006 Mineral of the Month: Strontianite by Karissa Hendershot
December Mineral of the Month: Clinozoisite
November Mineral of the Month: Bismuth
October Mineral of the Month: Wulfenite by Karissa Hendershot
September Mineral of the Month: Turquoise
August Mineral of the Month: Peridot
July Mineral of the Month: Ruby
June Mineral of the Month: Antarctic Fluorite
May Mineral of the Month: Dolomite, Part 2
April Mineral of the Month: Dolomite, Part 1
March Mineral of the Month: Calcite
February Mineral of the Month: Agate
January Mineral of the Month: Fluorite
December Mineral of the Month: Pyrite
November Mineral of the Month: Stilbite  
October Mineral of the Month: Celestite   

 

Comments and questions: kencasey@delminsociety.net

This page last updated:  February 19, 2011 10:15:15 AM

 

       

  


Next Meeting
 

April Program, Monday, April 8, 2013:

"Destruction of the Fossil Exposures in the Chesapeake Bay Area" presented by Dr. Lauck Ward

General Club Meeting:
April 8, 2013
(Monday)

We are meeting at
Greenbank Mill


Special Meetings:
 

*Show Committee Meeting, April or May, 2013

*New Home/Lapidary Committee, 2013

*Board Meeting,  April, 2013

Next Field Trips
 

Fieldtrips!

Past Fieldtrips
 

Next Show
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 Report

Updates!

 

 

 
Articles

 

Fossil Forum


"Dinny, the Dino"

"Belemnites are coming"

 

MOTM June also commemorates our 50th Show!

It's shiny, yellow, and is a symbol of 50 Years!Can you guess?

Past MOTM

Collecting Adventure Stories:

"Sunny Brook Crick Goethite" by Joe Dunleavy