
Rockhounding Delaware
Delaware is okay state for rockhounding. Delaware occasionally is referred to as "The Diamond State" because Thomas Jefferson once referred to it as a jewel due to its geographic location. There are, however, no diamonds there. Delaware does have a variety of fossils and some petrified wood. In addition, the state has some interesting mica specimens.
State Rocks, Gemstones, Minerals, Fossils, & Dinosaurs
Rockhounding Tip: Knowing state rocks, gemstones, minerals, fossils, and dinosaurs often can be very useful information for rockhounders. Ordinarily, states with significant mineral deposits, valuable gemstones, fossils, or unusual or significant rock occurrences will designate an official state mineral, rock/stone, gemstone, fossil, or dinosaur to promote interest in the state’s natural resources, history, tourism, etc. Accordingly, such state symbols often are a valuable clue as to potential worthwhile rockhounding opportunities.

Sillimanite
State
Mineral: Sillimanite (1977)
Delaware designated sillimanite as its official
state mineral in 1975. Sillimanite is aluminum
silicate that occurs in high temperature, aluminum-rich metamorphic rocks. Sillimanite is a polymorph with kyanite and
andalusite. It may take the form of
clear or gray-white glassy crystals or form fibrous masses with a silky luster. In Delaware, sillimanite is widespread
throughout the schists of the Delaware Piedmont and occurs as large masses and
stream-rounded boulders at the Brandywine Springs State Park. Sillimanite has no industrial value and is not
mined as an ore or raw material. The
mineral is named is in honor of Benjamin Silliman, a professor of Chemistry and
Natural History at Yale University from 1802 - 1853.

Belemnite fossils
State Fossil: Belemnite (1996)
Delaware designated belemnite as its
official state fossil in 1996. The belemnite was, in essence, a squid with a
conical shell. It is an extinct member
of the phylum Mollusca, which includes clams, snails, squids and octopuses. Belemnite fossils can be found in dredging piles from the creation of the Chesapeake and Delaware Canal.
Rockhounding Resources

State-specific rockhounding books (including the books listed here as well as other books), regional rockhounding site guides, and other helpful rockhounding resources are identified - by category - in the Books & Gear section of Gator Girl Rocks with a link to the Gator Girl Rocks Amazon Store where you may easily browse selected resources and securely place an order. Your order will benefit Charity Rocks!

Delaware
Geological Survey
Good information on cretaceous fossils
found in Delaware. The DGS also has
special publications pertaining to Delaware rocks, minerals, and fossils.

Delaware
Mineralogical Society
Website for the Delaware Mineralogical
Society. This rockhounding club has a
very useful website.
- John Means, Roadside Geology of Maryland, Delaware, and Washington DC (2010).
- James Martin Monaco & Jeannette Hathway Monaco, Fee Mining & Mineral Adventures in the Eastern U.S. (2d ed. 2010).
- Kathy J. Rygle & Stephen F. Pedersen, Northeast Treasure Hunter's Gem & Mineral Guide (4th ed. 2008).
Museums of Interest to Rockhounders

University of
Delaware Mineralogical Museum
University of
Delaware – Newark, Delaware
The Mineralogical Museum in Penny Hall
originated with the gift of the Irenée du Pont, Sr. collection in 1964. A significant part of this collection was
purchased in 1919 by Mr. du Pont from George Kunz, Vice-President of Tiffany
& Co, and had been on display in the Tiffany showroom in New York City.

Delaware Museum Of
Natural History
Wilmington,
Delaware
The Delaware Museum of Natural
History’s Dinosaur Gallery showcases the only dinosaurs on permanent display in
the state. The towering dinosaur
skeletons, Tuojiangosaurus and Yangchuanosaurus, represent Asian
relatives of the familiar North American dinosaurs, Stegosaurus and Allosaurus.
A Parasaurolophus head and Archaeopteryx
are also on display. The Dinosaur
Gallery includes the Science in Action Lab, where volunteers prepare real
paleontology specimens for study and answer visitor questions.

Iron Hill Museum
Delaware Academy of Science – Newark, Delaware
The museum houses part of the du Pont Rock and Mineral collection, which
displays rocks and minerals from around Delaware and around the world. In
addition, the museum’s exhibits include iron mining, petrified wood, fossils,
and fluorescent minerals.
Places to Visit - Interesting Sites To See
Brandywine Blue Granite
Brandywine Creek State Park – North of Wilmington,
Delaware
Wilmington blue rock (Brandywine Blue Gneiss of the Wilmington Complex) is
visible in the park. Naturally, the
rocks will appear dark gray or black, but, when quarried and fresh cuts are
exposed, the rocks have a bright blue color.
Garnets occur in the blue gneiss.

Swedes Landing
Swedes Landing
Wilmington, Delaware
This site is where the initial Swedish landing
took place and where the New Sweden colony began. In 1638 two
ships (the Kalmar Nyckel and the Fogel Grip) sailed up the Christina River past
the entrance to the Brandywine to "The Rocks" where a large flat slab
of blue rock protrudes into the main channel of the river. The large flat slab of rock on which the early
settlers landed, although reduced to make room for river travel on the
Christina, is still a present in Swedes Landing Park. "The Rock" is a
slab of Wilmington Complex gneiss or blue rock, and marks the eastern edge of
exposure of the Appalachian mountain system where the hard rocks of the
Piedmont Province plunge beneath the soft sediments of the Coastal Plain. The boundary between the Piedmont and the
Coastal Plain is defined in most places by a well-marked change in topography,
usually an abrupt transition from rolling hills to a flat smooth lowland.
Rockhounding Sites for Children & Families
Cretaceous Fossils
– Belemnite
Chesapeake and
Delaware Canal
Belemnite fossils can be found in the
exposures of the Mount Laurel Formation along the banks of the Chesapeake and
Delaware Canal in Delaware, east of St. Georges. The fine-grained sands and silts of the Mount
Laurel were deposited in a shallow sea during the Late Cretaceous time around
70 million years ago.
Muscovite Mica
Northern Delaware
Northern
Delaware has sites with muscovite mica that can form ‘mica books.’ The Woodlawn Quarry is a well-known site.