Delaware mineral enthusiasts! This month, our
First State to find biotites.
Spring is here, but bring a warm jacket. The weather promises to be
sunny today, so
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
from the Survey's suggestions, coupled with our club's and this author's field
Our article will landscapes.
In December 2007, we looked at Delaware Muscovite Mica. This month
we’ll visit Delaware Biotite Mica. It is a phyllosilicate with almost
perfect basal cleavage, and is found in a variety of igneous and
metamorphic rocks in The First State.
It was named after French physicist Jean-Baptiste Biot, who in 1816,
studied it’s unique properties. Today, the IMA has reclassified Biotite
as a group of micas, which contain phlogopite, siderophyllite, and
eastonite. These iron micas may be found in and around Delaware.
Eastonite, can be located at the C. K. Williams Quarry in Easton,
Biotites can be found at the old Wooddale Quarry and Woodlawn Quarry
in New Castle County.
With a hardness of 2.5-3, and a dark gray to black coloring, it is
relatively easy to identify it in the field. Biotites form at different
conditions than Muscovite in Bowen’s Reaction Series. It forms at a
higher temperature and with a more mafic composition than Muscovite.
Therefore, Biotites crystallize before Muscovite as magma cools.
So come on along, we have another Delaware Mica fieldtrip to make!
Mineralogically, the biotite gneisses are composed of plagioclase,
quartz, biotite, and iron oxides. Garnet, sillimanite, and
orthoclase in various combinations are also present in the samples.
Accessory minerals are zircon, sphene, and apatite. Some of the
plagioclase grains are antiperthitic.
Megascopically there are two varieites of biotite gneiss, (1) a
coarse-grained variety with flaser texture in which biotite defines a
strong foliation, and (2) a fine-grained variety, a granofels, with
small shredded grains of biotite in random arrangement. The
coarse-grained variety usually contains garnet, sillimanite, and
orthoclase; however, these minerals may also be present in small amounts
in the fine-grained lithology. Contacts between the coarse and
fine-grained phases are always sharp and may have elongated
poikiloblastic garnets concentrated among them."
Harmony Road, Wilmington Complex,
Biotite-bearing felsic gneiss
Our local . Please do join us!
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.
grab your walking sticks, and let's hike!
Easy to find garnet in host
(Photo by Ken Casey)
What's in a name?
Biotite was named by
J.F.L. Hausmann in 1847 in honour of the
Jean-Baptiste Biot, who, in 1816, researched the optical properties
of mica, discovering many unique properties.
The name “quartz” was grandfather prior to
1959 by the IMA.
silicate of chemical formula
Moh’s Hardness Scale,
it ranges from 6.5-7.5.
Biotite - K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2
Phlogopite - KMg3(AlSi3O10)(F,OH)2
Both Biotite and Phlogopite are mentioned in the DGS's
Catalog of Delaware Minerals
Biotite is a common
within the mica
group, with the approximate chemical formula K(Mg, Fe)3AlSi3O10(F,
OH)2. More generally, it refers to the dark mica series,
primarily a solid-solution series between the iron-endmember
annite, and the magnesium-endmember
more aluminous endmembers include
Biotite is a sheet
silicate. Iron, magnesium, aluminium, silicon, oxygen,
and hydrogen form sheets that are weakly bond together by potassium
ions. It is sometimes called "iron mica" because it is more iron-rich
than phlogopite. It is also sometimes called "black mica" as opposed to
"white mica" (muscovite)
-- both form in some rocks, in some instances side-by-side.
Like other mica
minerals, biotite has a highly perfect basal cleavage, and consists of
flexible sheets, or
lamellae, which easily flake
off. It has a
monoclinic crystal system, with
tabular to prismatic crystals with an obvious pinacoid termination. It
has four prism faces and two pinacoid faces to form a pseudohexagonal
crystal. Although not easily seen because of the cleavage and sheets,
fracture is uneven. It has a
hardness of 2.5 - 3, a
specific gravity of 2.7 - 3.1,
and an average density of 3.09 g/cm³. It appears
when weathered. It can be transparent to opaque, has a vitreous to
pearly lustre, and a grey-white streak. In its weathered yellow, sparkly
form, it is a common type of “fool’s Gold” (Pyrite
is the official “fool’s Gold”). When biotite is found in large chunks,
they are called “books” because it resembles a book with pages of many
Biotite is found in a wide variety of
igneous rocks and
rocks. For instance, biotite occurs in the
Monzoni. It is an essential
in some varieties of
lamprophyre. Biotite is occasionally found in large
sheets, especially in
pegmatite veins, as in
Carolina. Other notable occurrences include
It is an essential constituent of many metamorphic
and it forms in suitable compositions over a wide range of pressure and
It is not industrially useful, but it is mined using quarrying and
underground mining (depending on the depth of the biotite) for
Phlogopite is often found in association with ultramafic intrusions
as a secondary alteration phase within
metasomatic margins of large
ultramafic to mafic layered intrusions.
In some cases the phlogopite is considered to be produced by autogenic
alteration during cooling. In other instances,
has resulted in phlogopite formation within large volumes, as in the
ultramafic massif at Finero, Italy, within the
Trace phlogopite, again considered the result of metasomatism, is common
xenoliths carried up by
and so phlogopite appears to be a common trace mineral in the uppermost
part of the
Earth's mantle. Phlogopite is encountered as a primary
the result of highly fluid-rich melt compositions within the deep
In the photos below,
of Appalachian mountains and plateaus overlooking Susquehanna
River at Red Hill, Hyner, PA (Photos by Ken Casey)
Garnet-laden drill core samples
(Photo courtesy of Oliver Holm,
There is biotite in most all of
the gneises of Delaware's Piedmont.
"This area is comprised on mafic
and felsic gneisses and amphibolites of the Wilmington Complex and the
metasedimentary gneisses in the Wissahickon, Cockeysville, and Setters
formations as well as the migmatitic gneisses and amphibolites of the
(Taken from “Minerals of Delaware” by Peter B. Leavens, in
1979, Transactions of the Delaware Academy of Science, 1976, Delaware
Academy of Science, Newark, Delaware)
Piedmont Unit, Silurian
Ardentown Granitic Suite (Sags)
Perkins Run Gabbroic Suite (Spgs)
biotite tonalite (Sbt)
Three lithologies have been identified
within the Baltimore Gneiss in the Mill Creek Nappe:
granitic gneiss, hornblende-biotite gneiss, and
with or without pyroxene.
Lack of exposure prevents these
lithologies from being mapped separately. Granitic
with swirling leucosomes and irregular, biotite-rich,
layers constitute approximately 75 to 80 percent of the
exposed rocks. Pegmatites are commonly associated with
the granitic gneisses and are exposed in a series of
quarries along the northwestern boundary of the
H o c k e s s i n - Yorklyn anticline (Wo o d r u ff and Plank,
P e t ro g r a p h y. The granitic gneiss is
quartz, plagioclase, biotite, and microcline. Minor and
accessory minerals are garnet, muscovite, magnetite,
ilmenite, sphene, apatite, and zircon (Wo o d r u ff and
1995). The plagioclase is chiefly oligoclase with
concentrated along grain boundaries. Much of the
gneiss is migmatitic.
The hornblende gneiss contains plagioclase, quartz,
hornblende, and biotite with/without orthopyroxene.
Accessory minerals are garnet, muscovite, clinozoisite,
perthitic orthoclase, iron-titanium oxides, sphene, and
apatite. Hornblende grains are pleochroic in shades of
brown-green and green.
The amphibolites are composed of subequal amounts
of hornblende and plagioclase with minor quartz, biotite,
clinopyroxene, and orthopyroxene (Wo o d r u ff and Plank,
P e t ro g r a p h y. The Setters Formation and the
Wissahickon Formation are difficult to differentiate
but they can easily be distinguished in thin sections
by identifying feldspars. Microcline with cross hatch
twinning and perthitic lamellae is the most abundant
feldspar in both pelitic and psammitic facies of the
Formation. This distinguishes the Setters Formation from
the Wissahickon in which plagioclase is the most
feldspar and untwined orthoclase is present in small
amounts. Other minerals in the pelitic and psammitic
of the Setters Formation are garnet, muscovite,
quartz, and biotite with minor plagioclase. Accessory
are iron-titanium oxides, zircon, sphene, and apatite.
Myrmekites of quartz and feldspar cluster along grain
boundaries of microcline. Heteroblastic grains of quartz
commonly recrystallized to smaller subgrains. The
shows extensive alteration to green clay, and biotite
may show alteration to chlorite. Sillimanite occurs as
acicular grains, and large prisms that lie across the
Modal analyses are published in Kuhlman (1975),
Woodruff and Plank (1995), and Plank and Schenck (1997).
Plank and Schenck (1997) compare the Setters in Delaware
and Pennsylvania with the Setters in Maryland.
biotite is unstable and breaks down to form garnet
a reaction such as:
biotite + sillimanite + quartz = garnet + orthoclase +
water (Tracy 1978) or the incongruent melting of biotite:
biotite + sillimanite + quartz + Na-plagioclase = garnet
+ Ca-plagioclase + melt (Calem, 1987; Alcock, 1989).
Mineral assemblages of biotite,
microcline, quartz, and plagioclase indicate the rocks
metamorphosed to the amphibolite facies.
The biotite tonalite occurs as rounded boulders
with light gray to buff colors on fresh and weathered
The tonalite is leucocratic and contains 15-25 percent
mafic minerals. The biotite tonalite can be
the Ardentown Granitic Suite in hand specimen by a
equigranular texture and the scarcity or absence of Kf
e l d s p a r. Chemically, the biotite tonalite differs
from Ardentown Suite rocks of comparable silica content
by weight) in having significantly lower K2O
(0.69 vs. about 3.5 weight percent), as well as some
diff e rences
in trace element abundances (Srogi, 1988).
In this report we have formally named eleven new rock
units, informally recognized two rock units, and
mapped rock units in the Delaware and southeastern
Pennsylvania Piedmont. We have redefined the Wi l m i n
g t o n
Complex to include all rocks associated with the
of a Paleozoic magmatic arc; five metaplutonic
and herein named the Brandywine Blue Gneiss,
Montchanin Metagabbro, Mill Creek Metagabbro, Barley
Gneiss, and the Christianstead Gneiss; three
units, the Windy Hills Gneiss, Faulkland Gneiss, and the
Rockford Park Gneiss; three igneous plutons, the
Arden Plutonic Supersuite (comprising the Ardentown
Suite, Perkins Run Gabbronorite Suite, and one lithodeme
biotite tonalite), the Bringhurst Gabbro, and Iron Hill Gabbro.
The systematic changes that reflect increasing intensity
of metamorphism can be observed in the field as pelitic
assemblages record the breakdown of muscovite to
and orthoclase, the breakdown of biotite and sillimanite
to garnet, and the incongruent melting of biotite to
and cordierite. Mafic assemblages in the Wi l m i n g t
Complex record the change from blue-green amphibole to
brown amphibole to pyroxene. Precise estimates of peak
temperatures are more difficult because the reaction
are a function of water pressure, which is unknown
and probably variable, and a higher pressure metamorphic
overprinting is present in the Wissahickon east of the
Wilmington Complex (Crawford and Mark, 1982;
Bosbyshell, et al., 1999). Attempts to estimate peak
temperatures and pressures based on mineral
assemblages in garnet-bearing biotite gneisses using
grids and various geothermometers and geobarometers
(1) Brandywine Blue
The layering in the Wissahickon wall rock is irregular and defined by
stringers of garnet, biotite and sillimanite in a mass of quartz and
feldspar. The garnets are dark red, either oval or round, and may be as
large as three quarters of an inch in diameter.
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.
Mineralogically the Wis sahickon formation is
characterized by a composition
indicating extreme metamorphism. The essential minerals
are quartz, orthoclase feldspar, oligoclase feldspar,
Piedmont pegmatite bodies between Newark and Yorklyn..."
The minerals present in the pegmatite dikes are quartz,
feldspar microcline, muscovite, biotite and iron-bearing
these, quartz and microcline are most abundant, making
up over 75 per
cent of the local bodies."
Common detrital minerals in the sands of the Coastal
Plain are quartz,
chert, feldspar and rnus covite , Other detrital
material occurring in small
quantities (genera.lly 3 per cent or less by weight) is
formed by a group of
so-called heavy minerals (s.g. 2.87 or more), suchas the
magnetite, ilmenite, and pyrite, and a great variety of
such as zircon, tourmaline, garnet, rutile and other
staurolite, kyanite, sillimanite, andalusite, chloritoid,
augite and diopside. Some minerals, particularly
biotite, have a specific gravity close to 2. 87 and may
be found both in the
light and heavy fractions of a sediment. The accessory
heavy minerals are
of no great importance insofar as most uses of sand are
where very low iron content is desired.
The fine grained clays are generally composed of a group
of clay minerals,
which consist largely of hydrous aluminum silicates.
illite, chlorite and montmorillonite are found in the Coastal Plain
The Baltimore gneiss is a "quartztzo-feldspathic gneiss,
biotite gneiss, biotite hornblende gneiss, and amphibolites".
"Highly metamorphosed biotite gneisses of the Wissahickon are often
impossible to distinguish from the biotite gneisses of the Baltimore
Gneiss. Features that characterized the Baltimore Gneiss are (1)
intense migmatization, (2) highly variable strikes of foliation, (3)
general absence of sillimanite and primary muscovite , and (4) relic
granuliate facies assemblages containing orthopyroxene."
The Wissahickon in Delaware contains some metasedimentary pelitic
gneisses with biotite, quartz, plagioclase (oligoclase to andesine), and
various iron-titanium oxides.
"...the redefined Arden Plutonic
comprising the Ardentown Granitic Suite,
Perkins Run Gabbronorite Suite, and one
lithodeme of biotite tonalite; and three
metavolcanic units named the Rockford Park
Gneiss, Windy Hills Gneiss, and Faulkland
"A mineral with perfect basal cleavage
that easily separates into
sheets. The varieties are black biotite, white
phlogopite, and green chlorite. Micas are common in all
rocks except the high-grade gneisses of the Wilmington Complex."
Baltimore Gneiss—represents the ancient North
American continent; rocks are interlayered granitic
biotite gneiss, pegmatite, and amphibolite.
In Delaware, the Baltimore Gneiss is a contorted mixture
granitic gneisses, biotite gneisses, amphibolites, and pegmatites.
Wissahickon rocks always show two types of layering that
are parallel to each other: (1) a gross layering between
rock units (e. g., between the gneisses and
(2) a fine light-dark compositional layering within each
unit (Figure 25 A and B). The gross layering is presumed
parallel to the original sedimentary beds, and the fine
is thought to be
a result of a
migrate to form a
light layer, while
the dark minerals,
biotite and sillimanite,
dark layer. Thus
the overall composition
rock remains the
same, but the
the original rock.
Figure 25. Layering in the Wissahickon
(A) Gross layering between black amphibolite
and light-colored gneiss.
(B) Fine compositional layering in the
gneiss, Wooddale Quarry; note the cross
cutting pegmatite pods.
Biotite is used extensively to constrain ages of rocks, by either
potassium-argon dating or
argon-argon dating. Because argon escapes readily from the biotite
crystal structure at high temperatures, these methods may provide only
minimum ages for many rocks. Biotite is also useful in assessing
temperature histories of metamorphic rocks, because the partitioning of
magnesium between biotite and
is sensitive to temperature.
Biotite is used in electrical devices, usually as a
Moving down this series you move from minerals that are
least resistant to weathering, or most easily broken down, to minerals
that are most resistant to weathering, or the hardest to break down. A
few things to note regarding this sequence: First, this sequence
includes only primary silicates.
Second, looking at the minerals, the most resistant
minerals are felsic while the least resistant minerals are mafic.
In a weathering environment like that in the southeast region of the
U.S. you essentially will not find mafic minerals in soil - they will
all have weathered away to secondary minerals. Quartz and muscovite
are more common in soils than any of the other primary silicates.
|Almandite Garnet crystal
Photomicrograph, South Carolina's Appalachian Piedmont
||Almandite Garnets the size of dimes in
Brandywine Creek State Park
Harmon Maher ; Photo by Ken
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
Generalized Piedmont Map; Piedmont is Tan
(Courtesy of Karl Musser, Cartographer, wikipedia.org
A rare igneous garnet is
found in the pegmatite of the
Woodlawn Quarry. The locale may be
in the red area of the
Generalized Geologic Map of Delaware, below.
Why not try this one:
Quarry: A GeoAdventure in the Delaware Piedmont
Generalized Geologic Map of Delaware, courtesy of the Delaware
Prepared by: Nenad Spoljaric and Robert Jordan, Revised by: Thomas E.
|Physiographic Map of
Pennsylvania, Pennsylvania Geological Survey
Yes, right in o
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,
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
opaques 1.0 RETROGRADE MINERALS
sillimanite mats x
Pale green mineral with opaques
NUMBER OF POINTS COUNTED: 400
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
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
If you like the smalle
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
||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
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
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
layers vary in thickness between
3 inches and 2 feet, and are dark
solid, massive rocks.”
Let's zoom in on our gneiss garnets.
|Large red garnets in
Rocky Run rock, BCSP
|Photos by Ken Casey
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
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
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.
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
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)
Pyroxenes (and amphiboles), Tourmaline and Garnet (UC Berkeley)
Quarry: A GeoAdventure in the Delaware Piedmont
Delaware Minerals List
Here is where DMS Members can add their Delaware
Quartz photos to share
|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.
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.
Arthur Koch, DMS Member, B. S. in Geology,
Nenad Spoljaric and Robert Jordan, Thomas E.
Pickett, Delaware Geological Survey
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
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
About the Author:
Ken is current webmaster of the Delaware
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
And, he is currently a member of the Delaware
Mineralogical Society and the Franklin-Ogdensburg
Mineralogical Society. E-mail: