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Calendar
of Events
Summer 2009
Download
a PDF of the Summer Newsletter HERE
Download
our Educational Brochure
(You
must have Acrobat Reader for these documents)
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Special
Exhibit “Worldwide Agates”
June 9 to September 6, 2009
See
the fascinating diversity of agates found around
the world. One of the most common gemstones, agates
are used in jewelry and treasured by collectors.
A geography activity for children accompanies this
exhibit.
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June
20 “Geode Colleting Field Trip”
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Collect
geodes near the Mississippi River in Illinois. A hilltop
quarry yields abundant and fascinating geodes. A geode
cracker will be on hand to open geodes in the quarry. Other
minerals and fossils are available to collect. Trip fees
include tour guides, collecting and cracking fees and motorcoach.
Field Trip – Ages 8 yrs. to Adult – 7
a.m. to 9 p.m.
Fee: $105.00 per person – Museum Members $100.00
Reservations Required: (630) 833-1616
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Pick
Up Your Passport to Adventure Here!
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Summer
is a great time to visit the museums in Kane and DuPage
Counties. Designed
for ages 4 to 12, each site has an activity for children
to complete. Visit 7 or more sites and win a prize! The
Summer Passport program begins Memorial Day and ends Labor
Day.
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July
11 “Fossil Discovery”
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This interactive
presentation allows children and adults to learn how fossils
are formed, where to look for fossils, and study fossils.
Activities include: a fossil quiz game to win prizes, polishing
amber, searching for shark teeth, and breaking casts for
dinosaur bones. Children can keep all the fossils they find
and win.
Interactive Lecture/Activity - Ages 7 yrs. to Adult
2 p.m. – 75
minutes
Fee: $15.00 per person, Museum Members $10.00
Reservations Recommended - 630-833-1616
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July
25 “Fossil
Collecting Field Trip”
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Travel by motorcoach to a quarry near Rockford, Illinois.
Collect Ordovician Period (450 million years old) marine
fossils in limestone. Collectable fossils include: brachiopods,
gastropods, corals, crinoids, trilobites and cephalopods.
Field Trip - Ages 8 yrs. to Adult - 8:00 a.m. to 3:00 p.m.
Fee: $37.00 per person, Museum Member $32.00
Reservations Required: 833-1616
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Every
Sunday Afternoon 3:00 p.m.
“ Collecting Earth’s
Natural Treasures”
50 minute video shows beginners information on starting a mineral and fossil
collection, where to search for specimens and how to cut and polish stones hosted
by Bob Jones.
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August
1 “Soapstone Carving”
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Lapidary Lorel Abrell teaches participants how to successfully
carve soapstone. Simple tools and techniques are used in
carving this soft and inexpensive material. Learn the basics
from blocking out a design to final polish. Take home a carving
of your own creation. All materials are included.
Activity - ages 9 yrs to Adult - 10 a.m. to 12 p.m.
Fee: $15.00 per person, Museum Members $10.00
Reservations Required: 630-833-1616
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August
16 “A World of Agates”
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Agate specialist Doug Moore presents his award winning
program on agates. Outstanding pictures explore agates from
notable locations in the U.S. and around the world. Learn
the general geology and specific characteristics of different
varieties, theories of formation and value. An entertaining
and educational program for all rockhounds.
Lecture – ages 9 yrs to Adult – 2 p.m. – 60
minutes
Regular Museum Admission, Reservations Recommended.
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September
26 “Fossil Dig”
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Learn about the world
famous Mazon Creek fossils from Illinois with Don Baumgartner.
These Coal Age fossils (350 million years old) are a unique
part of Illinois geologic history and the fossil record.
Learn where to collect these fossils and search for a Mazon
Creek fossil to take home.
Lecture/Activity - Ages 6 yrs. to Adult - 60 minutes - 2
p.m.
$4.00 per person, Museum Members Free - Reservations Recommended
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Special
Exhibit “Worldwide
Agates” June 9 to August 31, 2009
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Features over 40 agates of rare and more common origins found
around the world. Many agates from the United States and
Mexico are represented as well as South America, Africa,
Europe, Asia and Australia. Agate is a popular choice in
current jewelry trends. Learn more about this unique gemstone
at the lecture “A World of Agates” presented
by Doug Moore on Sunday, August 16 at 2pm.
About Agates
By Michael R. Carlson
Agates are among the most marvelous and varied works
of nature. Due to their availability, beauty
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Baker Ranch Thunder Egg
from New Mexico. |
and durability,
they have been collected and worked since time immemorial.
Gathered and kept as treasured objects, agates have long
been used and fashioned into such items as jewelry, charms,
seals, carvings, bowls, weapons, tools, bookends, marbles
and so on.
Agates exhibit an array of patterns and colors that no other gemstone can match.
Unlike other gems, each individual agate is unique in color and design. Agates
are cuttable, yet tough, and take a very high and lasting polish. They are
recognized by the general public, but also studied by scholars. Agates can
be seen in the finest museums, but are found as well on the shelves of amateur
collectors.
The world’s agates are widely distributed, and can be found in igneous,
sedimentary, and metamorphic areas. They have been collected from deserts,
mountains, rivers, and ocean shores. The word “agate” itself is
likely derived from the ancient Achates River in Sicily, where the first written
description of agates was found.
The basic material of agate (ag?it) is chalcedony (kal sed?’n e), which
is silicon dioxide (SiO2) in the form of microscopic fibrous crystals, called
cryptocrystalline. While pure chalcedony is typically colorless to white, agates
are a variegated form of chalcedony, which can range from translucent to nearly
opaque. Metallic salts or oxides primarily color them, with red, brown, yellow,
and gray the most common shades. Essentially, agate is a colored variety of
chalcedony, which can exhibit bands, dots, clouds, or moss-like formations.
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Crowley’s
Ridge agate from Arkansas.
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Other physical characteristics of agates include: a glassy or waxy appearance,
no cleavage direction, a shell-like conchoidal fracture, and a specific gravity
near 2.60. The hardness of agates varies around 7 on the Mohs scale. Agates
are somewhat porous, which allows them to be dyed with various chemicals and
acids. Fluorescence of agates is rare, and is usually greenish if it occurs.
Although many agates are found as nodular varieties, agates can also be found
in other forms such as veins, or replacements of wood and coral.
There are several differing theories of banded agate formation, but no single
theory has yet accounted for all of the varieties and structures exhibited.
Generally, however, there must have been a deposition of silica into vesicles,
or chambers, formed in surrounding rock. Ground waters possibly dissolved the
silica from the host rock in which the agate was formed. This silica was likely
to have been gelatinous for a period of time. Because agates are more resistant
than the surrounding rock, they are usually released over time by weathering
processes.
Agate Quality
While beauty may indeed lie in the eye of the beholder, there are certain features
that help top agates stand apart from the rest. These observable traits can
be divided into several noteworthy categories including pattern, color, shape,
size, and rarity. Other defined unique characteristics can also influence
perceived quality.
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Laguna agate from
Chihuahua,
Mexico.
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Pattern refers to the overall design of the banding. The pattern may be regular
and concentric, or it may be more free form in nature. The best stones are
usually the ones with a strong pattern and contrasting colors. Whole and complete
patterns are much preferred over broken ones.
The color of an agate will greatly affect its overall quality.
The coloring may be bright, subtle, or a combination of each. Agates
showing several strong
colors are often the most desirable, especially if these colors
are intense or unusual.
The shape of the agate can add or detract from its appeal. If the
shape is not pleasing as a whole, then the effects of banding,
color, and other features
will be diminished. Complete shapes are far more preferable than
broken ones. Shape gives definition and presence to the stone.
Size may not be as relevant to a stone’s quality as other attributes,
but top agates of large size can be eye catchers. Maximum size does vary
among the many varieties of agates. Queensland agates, for example, are generally
quite small, with most being under one-half pound. Brazilian agates, on the
other hand, are quite often several pounds in size.
Solidity (lack of fractures, crystalline quartz, and matrix) also helps determine
the quality of the agate. All varieties of agates are to some degree affected
by fractures or cracks. There are many different causes of this fracturing.
Regardless of the reason, cracks can impair stones of otherwise top quality.
All agates are a variety of quartz, but the amount of crystalline
quartz seen can also affect their appearance. Generally less visible
quartz of this type
is preferred, although it may occasionally enhance the look of
an agate. For example, quartz geode centers can add an extra sparkle
to some stones.
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Lake Superior agate “Laker” from
Minnesota.
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Matrix can also detract from the general appearance of an agate. Agates that
show large amounts of their host matrix material are usually not as appealing
as specimens that are composed entirely of agate. An exception might be an
agate nodule still largely enclosed in the matrix in which it was formed. This
type of specimen can yield valuable insight into the formation process.
Choice combinations of top pattern, bright colors, good shape, large size,
solidity, and unique characteristics are indeed rare. Most exceptional agates
include several or all of these features.
This article was excerpted from The Beauty
of Banded Agates An Exploration of Agates from Eight Major Worldwide Sites by Michael R. Carlson. The book
is available in the Museum Gift Shop and online at www.agate-nodule.com.
Many thanks to Mike Carlson, Austen Cargill and Doug Moore for their help
in putting
together the special exhibit “Worldwide Agates.”
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Scout
Badges & Educational Programs
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Geologist,
Museum Educator and Boy Scout Merit Badge Counselor,
Sara Johnson conducts programs at the Museum that count
toward the completion of Merit Badges for Scout groups.
Webelos in Cub Scouts can earn their Geology Badge,
Boy Scouts their Geology Merit Badge and Junior Girl
Scouts their Rocks Rock Badge. Programs include rock
and mineral identification, careers in earth science
and the uses of rocks and minerals in everyday life.
A general tour of the Museum is a good way to get started
familiarizing your group with rocks and minerals. Additional
educational programs are useful for small groups such
as home schools and Science Olympics events. Outreach
programs are available to schools. To schedule a group
tour, additional educational activity or outreach program
call the Museum (630) 833-1616 or email Sara Johnson
at info@lizzadromuseum.org.
Educational and outreach
program support provided in part through a grant from
the DuPage Community Foundation.
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Educational
Boxes Available
The Museum offers educational boxes with
rocks, minerals, and fossils, hands-on
specimens and activities. Three boxes are
available for
loan: Rocks& Minerals, The Quartz Family, and Illinois Rocks& Minerals.
Geared for 3rd thru 6th grade, boxes are loaned free of charge
to groups; school, scout, home schools, camps and day cares. Call
or e-mail the Museum
for an educational brochure.
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Download
a PDF of the Summer Newsletter HERE
Download
our Educational Brochure
(You
must have Acrobat Reader for these documents)
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