Filed under: regular postings — Gary July 27, 2010 @ 9:37 pm

gemology links in alphabetical order

Accredited Gemologists Association
is a nonprofit research, education and ethics organization benefiting professional and avocation gemologists as well as consumer interest

Alexandrite Gemstone Buyer and Collectors Guide
history, sources, valuation and collection of alexandrite gemstones. Topics also include chemical and physical properties, mythology, and color change phenomena as well as alexandrite synthetics and imitations

American Gem Society
m embers of the American Gem Society are dedicated to providing the most knowledgeable service to their customers

American Gem Trade Association
the AGTA is an association of US and Canadian colored gemstone and cultured pearl industry professionals dedicated to promoting the natural colored gemstone trade

Asian Institute of Gemological Sciences (AIGS)
located in Bangkok, Thailand, founded in 1978 as Southeast Asia’s first educational and research institute devoted exclusively to the training of students in the scientific and practical aspects of gemology and the gem trade

Canadian Gemmological Association
Canada’s professional organization for the practice of gemmology. Website contains information about the organization, including information on membership, products, meeting times, annual Gem Conferences and more.

Centre de Recherche Gemmologique
the Gemological Research Center at the University of Nantes

Italian centre for information and services in gemmology. As well as carrying out its principal work of analysis, the Centre provides extensive information on gemmology, through courses, conferences, publications

DeMello Gemological National Laboratory
Providing expert gemological testing and related appraisal services for consumers, gemstone buyers, collectors, legal counsel and law inforcement

Europe’s leading institute for training and research concerning gemmology since 1932

L’Ecole des Gemmes
Centre de formation qualifiante en gemmologie. Allied teaching center of the Gemmological Association of Great Britain in France.

Field gemology
dedicated to people sharing an equal passion for gems, gemology and traveling

Gem and Jewelry Institute of Thailand
Bangkok-based government gem lab and school

gemological laboratory based in the Principality of Liechtenstein offering laboratory services

Gemlab Inc.
Research and development high-tech gem treatment laboratory, short courses in gem treatments, fabrication of gem instruments and gem treating equipment, books, etc.

Gemmes Inclusions
Photographs of inclusions in gemstones. Also covers treated stones, syntheses, doublets.

Gemmological Association and Gem Testing Laboratory of Great Britain
gives details of courses, tutotials, workshops, exam details and dates, trips and other special events, lectures etc.

Gemmological Association of All Japan
Japan’s leading gemmological educational institution

Gemmological Association of Australia
Australia’s traditional gemmological educator since 1945

Gemmological Society of South Africa
promotes fair trade and full disclosure by all gemstone traders

Gemmology in Scotland
Scottish Branch of the Gemmological Association

Gemmology World
Canadian Institute of Gemmology

Gem Nantes Gemmologie à Nantes
diverses formations en gemmologie (DUG et programmes courts) et les activités de recherche scientifique en gemmologie

The Gemology Project
non-profit gemstone and gem science wiki-style database for anyone interested in gemstones and gemology

Gemstone Identification Chart
analyze the results got with the refractometer, polariscope, dichroscope, spectroscope, UV light, dichromatic filter, density scale, microscope and loupe, hardness tester

is an online guide to gemstone prices

GIA – Gemological Institute of America
the world’s largest and most respected nonprofit institute of gemological research and learning

Gübelin Gemmological Laboratories
Swiss gemmological laboratory

HRD (Hoge Raad voor Diamant)
Diamond High Council, Antwerp, Belgium

Instituto Brasileiro de Gemas e Metais Preciosos
private, non-profit association of Brazilian gemstone, jewellery and related industries

Institut Gemmologique de France
French gemological institute

Institut National de Gemmologie
The National Institute of Gemmology teaches over 500 persons a year and gives certifies over 100 persons each year (Brevet Professionnel, FEEG, Diploma of ING)

Instituto Gemológico Español
Spanish gemological institute

International Colored Gemstone Association
a non-profit association to represent the international gemstone industry

International Gem Society
dedicated to bringing quality information and educational services to everyone interested in gemstones

collection of gemstone related information like buying guide, recource directory, info on different gemstone species, etc.

Portuguese gemological laboratory

Laboratoire français de Gemmologie
French gemological laboratory in Paris
information on gemstones, collector stones and rare facetable minerals

Russian Gemological Server
information on business, research and educational projects in gemology

Swiss Gemmological Institute
part of the Swiss Foundation for the Research of Gemstones, founded by trade organisations in 1974 and works independently on a scientific basis

Boston Mineral Club

Filed under: Club Rollcall (hello's) — Gary @ 9:33 pm

Hello Boston Rockhounds!

The Boston Mineral Club (BMC) was founded in 1936 to “promote the study and collecting of rocks and minerals, to encourage friendly cooperation among mineralogists and collectors, [and] to promote the study of mineralogy and related arts and sciences coming within the purview of earth sciences…” In the pursuit of these goals, the BMC offers educational programs at club meetings, mineral collecting field trips, a newsletter, and access to our mineralogical reference library.

The Boston Mineral Club is a member of the American Federation of Mineral Societies and the Eastern Federation of Mineral and Lapidary Societies.

You do not need a college degree in earth sciences to join the club! We are open to all. We welcome and encourage new members to join the club.

Ancient Egyptians Inhabit the Grand Canyon?

Filed under: regular postings — Gary July 25, 2010 @ 9:56 pm

True or not, pretty interesting :)



Remember how disgusted you felt when, in the closing scene of the film, Raiders of The Lost Ark, the Ark of the Covenant – hidden in an anonymous wooden crate – was consigned to a giant warehouse full of similar looking crates? Your reaction was ‘Cover up by the government!’ – no doubt. This was fiction, but do such cover-ups really happen?

One of the most revered historical institutions in the USA, if not the world, is the Smithsonian Institute, compilers and keepers of American history for as long as anyone can remember. Would they – could they blatantly ignore the existence of a staggering historical find, because it seemed too radical for conventional thinking? People must judge that for themselves.

One of the greatest natural wonders of the world cuts deep into the heart of Arizona – the Grand Canyon. Beautiful and breathtaking, this vast cleft in the earth holds many secrets, perhaps none more mysterious than the one reported in the Phoenix Gazette, on April 5th 1909. An explorer, one G.E. Kincaid (who had served the Smithsonian for over thirty years) was reporting a startling archeological discovery.

Grand Canyon

Kincaid’s boss, Professor S.A. Jordan of the Smithsonian – who were financing the expedition – was said to be enthusiastic that the find be further investigated, as it was of ‘major significance’. Kincaid had found, about 2000 feet up the canyon wall above the Colorado river – some forty-two miles upstream from the El Tovar crystal canyon – a cave entrance to a vast underground city, chiseled from the solid rock.

There were steps up to the cave, suggesting that the river level had been that high when the inhabitants had lived there. This would mean at least 3000 years had passed since then! This citadel was almost a mile underground, and was very precisely carved, in geometric patterns, over an enormous area. Kincaid reported that several hundred rooms had been discovered, but that the full extent of the ‘city’ was still impossible to estimate.

Perhaps the most startling find was the great hall, about 100 feet in from the cave entrance. This contained a carved idol (presumably of the god these people worshipped), which he described thus: The idol sits cross-legged, with lotus flower or lily in each hand. The cast of the face is oriental, and the carving shows a skilful hand, being remarkably well preserved. It resembles Buddha, and though scientists are unsure of its religious import, it reminds them strongly of the ancient people of Tibet.

Many smaller, beautifully carved images were reported, as was the finding of all kinds of copper tools – preserved by some hardening method, which modern day scientists have failed to emulate. Artistic vases and urns of copper and gold as well as enameled ware and glazed vessels were found. Granaries, like those found in oriental temples, and still holding seeds, were also discovered.

There was a grey metal found, resembling platinum, which scientists could not identify, and yellow stones, known as ‘cat’s eyes’, were everywhere, each one engraved with a Malay type head. Even more significant was the finding of hieroglyphics – amazingly similar to those found in Egypt – engraved on urns, on tablets and around doorways. Deciphering these would be a major step toward solving the mystery; but did it ever happen?

A large crypt was found, with many mummies in it, reportedly well preserved. They were all male, entombed with weapons, suggesting that this was a burial site for soldiers – though varying degrees of development in the ceramics found with them hint that this was a civilization that was constantly refining itself. It was thought that up to 50,000 people could have lived in this city.

Strangely enough, the tradition among the Hopi Indians tells of an ancestry that harks back to their people having once lived in an underworld in the Grand Canyon, until rivalry broke out between two factions. The good faction – the people of one heart – were led to the outside world by their chief, Machetto – while the people of two hearts remained behind.



The Isis Temple, Grand Canyon

Today, visitors looking from the South Rim of the Canyon can see the structure called ‘The Isis Temple’ – a pyramid hewn from the solid rock of the cliff top, and obviously man-made. Page 302 in the book, Ancient secrets of the Flower of Life Vol II, holds an account, by two backpackers, of an exploration of this edifice.

They tell of finding cave entrances that had been deliberately sealed, though they did seem man made, one having a clear, 6ft circular pattern carved into the roof. This site is over 40 miles from the one reported in the newspaper article – yet why would caves that are almost inaccessible need to be sealed up, and was the originally stated location simply a mistake?

G.E. Kincaid was a respected man, the first white child born in Idaho, and an explorer for all of his life. His words about the entrance to the citadel are prophetic: ‘First, I would impress that the cavern is nearly inaccessible, he said. The entrance is 1,486 feet down the sheer face of the canyon wall. It is on government land, and no visitor will be allowed, under penalty of trespass. A trip there would be fruitless, and the visitor sent on his way. I sent a number of relics to Washington, after which the exploration was undertaken.’

In the latter part of the twentieth century, detailed research by one Carl Munck uncovered a mathematical system, employed by the ancients for the exact placement of the Egyptian pyramids in alignment with certain star systems. This same code can be applied to other such structures, wherever they are found. His findings revealed that the Isis Temple must be a major archeological site, lined up as precisely as it is with the great pyramid of Giza.

Great Pyramid, Giza Egypt

In 1909, the Grand Canyon citadel was regarded as not only the oldest archeological discovery in the United States, but also as one of paramount importance to the world, yet today, nothing more is known to the public than has already been said. The Grand Canyon is festooned with places that bear ancient Egyptian names, yet no one in authority can tell you why.

Interest in the area is highly discouraged by officialdom, and the Smithsonian Institution claim to have no record of Kincaid, Professor Johnson or a lost Egyptian civilization in Arizona. The Phoenix Gazette story must have been a hoax; or could it be that something was discovered, back then, of such monumental import that it needed to be ‘hushed up’ for evermore?

Did G. E. Kincaid actually exist? With no records of his work, or any proof from the Smithsonian that he worked for them, many think the newspaper article was an April Fool’s Day joke! However, the above copy of an earlier newspaper piece from 1909, published a whole month before the Phoenix Gazette piece appeared, shows that G.C. Kincade’s expedition did indeed happen as reported!

What is more, a translated ancient manuscript, recently located, describes a voyage made thousands of years ago by a group from Asia travelling to a city built within what they called ‘The Canyon of Light’, intending to visit a holy man, or shrine. The descriptions given seem to indicate that this city was to be found in the Grand Canyon!

The Nile

No one is prepared to answer the questions that all of this poses, even though the research done within the citadel might have proved, beyond doubt, that the race which built it were of oriental origin, possibly Egyptian travelers from the time of Rameses. Hieroglyphs found in Australia point unequivocally to Egyptians having been there at some time, so why not the Americas as well?

Perhaps the Nile, the Colorado and the Grand Canyon are inextricably linked through a span of time that defies the imagination, but if so, someone has decided that we should never know how strong those links are. The citadel may, officially, be no more than an elaborate myth, but the evidence for a contrary view is quite compelling.

It would, perhaps, be unfair to put the ‘lost’ underground city into the same category as Area 51, but the secrecy surrounding it over ninety years can’t help but make you wonder just what was actually discovered. Unfortunately for the enquiring minds amongst us, we may never know.


Egyptian Artifacts in the Grand Canyon
The Phoenix Gazette – April 5, 1909

click here

Green River

Green River

With gratitude to Steve Wingate

for his own efforts at finding this cave and our combined effort to solve this mystery.

An Analysis on the Probable Location of an “Underground Citadel”

Alleged to be in the Grand Canyon of the Colorado River, Arizona,

according to a “Phoenix (Arizona) Gazette” front page news story dated “April 5, 1909″

First published June 27, 2001 at: “Lost Civilizations and Hidden Mysteries”

Exploration and Imagination with Jack Andrews and Susan Anway:

I have known of this location since 1972.

I have held the secret since then.

I feel it is the proper time to reveal the location.

Jack Andrews June 27, 2001

click here




Pyrite or Foolsgold

Filed under: Mineral of the day — Gary @ 9:16 pm


The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral’s metallic lustre and pale-to-normal, brass-yellow hue have earned it the nickname fool’s gold because of its resemblance to gold. The color has also led to the nicknames brass, brazzle and Brazil, primarily used to refer to pyrite found in coal.

Pyrite is the most common of the sulfide minerals. The name pyrite is derived from the Greek πυρίτης (puritēs), “of fire” or “in fire”, from πύρ (pur), “fire”. In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel; Pliny the Elder described one of them as being brassy, almost certainly a reference to what we now call pyrite. By Georgius Agricola’s time, the term had become a generic term for all of the sulfide minerals.

Pyrite is usually found associated with other sulfides or oxides in quartz veins, sedimentary rock, and metamorphic rock, as well as in coal beds, and as a replacement mineral in fossils. Despite being nicknamed fool’s gold, pyrite is sometimes found in association with small quantities of gold. Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin, Nevada, gold deposit, arsenian pyrite contains up to 0.37 wt% gold. Auriferous pyrite is a valuable ore of gold.

Weathering and release of sulfate

Pyrite exposed to the atmosphere during mining and excavation reacts with oxygen and water to form sulfate, resulting in acid mine drainage. This acidity results from the action of Acidithiobacillus bacteria, which generate their energy by oxidizing ferrous iron (Fe2+) to ferric iron (Fe3+) using oxygen. The ferric iron in turn attacks the pyrite to produce ferrous iron and sulfate. The ferrous iron is then available for oxidation by the bacterium; this cycle continues until the pyrite is depleted.

Iron pyrite oxidation is sufficiently exothermic that underground coal mines in high-sulfur coal seams have occasionally had serious problems with spontaneous combustion in the mined-out areas of the mine. The solution is to hermetically seal the mined-out areas to exclude oxygen.

In modern coal mines, limestone dust is sprayed onto the exposed coal surfaces to reduce the hazard of dust explosions. This has the secondary benefit of neutralizing the acid released by pyrite oxidation and therefore slowing the oxidation cycle described above, thus reducing the likelihood of spontaneous combustion. In the long term, however, oxidation continues, and the hydrated sulfates formed may exert crystallization pressure that can expand cracks in the rock and lead eventually to roof fall.

Building stone containing pyrite tends to stain brown as the pyrite oxidizes. This problem appears to be significantly worse if any marcasite is also present. The presence of pyrite in the aggregate used to make concrete can lead to severe deterioration as the pyrite oxidizes. In early 2009, problems with Chinese drywall imported into the United States after Hurricane Katrina were attributed to oxidation of pyrite.




Pyrite enjoyed brief popularity in the 16th and 17th centuries as a source of ignition in early firearms, most notably the wheellock, where the cock held a lump of pyrite against a circular file to strike the sparks needed to fire the gun.

Pyrite has been used since classical times to manufacture copperas, or iron sulfate. Iron pyrite was heaped up and allowed to weather as described above (an early form of heap leaching). The acidic runoff from the heap was then boiled with iron to produce iron sulfate. In the 15th century, oil of vitriol (sulfuric acid) was manufactured either from copperas or by burning sulfur to sulfur dioxide and then converting that to sulfuric acid. By the 19th century, the dominant method was to burn iron pyrite. Pyrite remains in commercial use for the production of sulfur dioxide, for use in such applications as the paper industry, and in the manufacture of sulfuric acid. Thermal decomposition of pyrite into FeS and elemental sulfur starts at 550 °C; at around 700 °C pS2 is about 1 atm.

Pyrite is a semiconductor material with band gap of 0.95 eV.

During the early years of the 20th century, pyrite was used as a mineral detector in radio receivers, and is still used by ‘crystal radio’ hobbyists. Until the vacuum tube matured, the crystal detector was the most sensitive and dependable detector available- with considerable variation between mineral types and even individual samples within a particular type of mineral. The most sensitive mineral was galena, which was very sensitive also to mechanical vibration, and easily knocked off the sensitive point; the most stable were perikon mineral pairs; and midway between was the pyrites detector, which is approximately as sensitive as a modern 1N34A diode detector.

Pyrite has been proposed as an abundant inexpensive material in low cost photovoltaic solar panels.Synthetic iron sulfide is used with copper sulfide to create the experimental photovoltaic material.[21]

Pyrite is used to make marcasite jewellery (incorrectly termed marcasite). Marcasite jewellery, made from small faceted pieces of pyrite, often set in silver, was popular in the Victorian era.



Color Pale brass-yellow, tarnishes darker and iridescent
Crystal habit Cubic, faces may be striated, but also frequently octahedral and pyritohedron. Often inter-grown, massive, radiated, granular, globular and stalactitic.
Crystal system Isometric Diploidal, Space group Pa3
Twinning Penetration and contact twinning
Cleavage Indistinct on {001}; partings on {011} and {111}
Fracture Very uneven, sometimes conchoidal
Tenacity Brittle
Mohs scale hardness 6–6.5
Luster Metallic, glistening
Streak Greenish-black to brownish-black; smells of sulfur
Diaphaneity Opaque
Specific gravity 4.95–5.10
Fusibility 2.5–3 to a magnetic globule
Solubility Insoluble in water
Other characteristics paramagnetic

Thanks wikipedia

Test For Gold In Pyrite

Filed under: regular postings — Gary @ 9:04 pm



In a nugget patch I’ve been working there is vein of green stone(chorite shist). It really sounds off my metal detector. I think it is loaded with pryrite. Is there a simple test for gold I can do? Also around this vein is decomposed bedrock that has a lot of black sand, not much gold. Could this sand contain gold that isn’t
visible to the eye? Any suggestions?


For iron pyrite (sulfide), here’s the test:

(In a ventilated area… using a small sample)

Crush and roast the sample at high heat.

When iron sulfide is roasted, the sulfur vaporizes and results in iron.

The iron will pick up with a magnet.

Check this website out for a full answer:

“The reason most prospectors know a lot about the appearance and habits of iron pyrite is twofold:
1) To keep from being fooled.
2) Because of the known association between pyrite and gold. Pyrite is found in, or asociated with,
more than 70% of the world’s gold deposits.”

Rockhound locations and stories wanted…

Filed under: regular postings — Gary @ 8:31 pm

I am looking to post about rockhounding places/trips from my readers-if its rockhounding, I’m interested!!!

Also stories as well as rockhounding news or just a shout from a local rockhound club.  My blog is as good as my submissions!


Diamond Saw

Filed under: how to? — Gary July 20, 2010 @ 6:27 pm
Diamond Saw

Diamond Saw

Diamond Saw Wont Cut- If your blade still has diamond on it, and won’t cut, run a brick, concrete, old aluminum oxide grinding wheel, or Obsidian about 3″ thru the blade. This will strip off any alloy that is covering the diamond particles allowing them to cut. If you have no diamond left, you need a new blade.

Keeping the Oil Out -If you suspect that the rock you are about to cut will soak in oil, you should soak the rock in water for at least 24 hours before cutting. This fills the porous areas with water. Cutting oil can stain some stones. Denim Lapis is an example. Soaking in water really helps to minimize oil soak in.

AUSTINITE – Gold Hill, Utah

Filed under: regular postings — Gary July 19, 2010 @ 10:03 pm


Austinite is a member of the adelite-descloizite group, adelite subgroup, the Zn end member of the Cu-Zn series with conichalcite. It is the zinc analogue of cobaltaustinite and nickelaustinite. At one time “brickerite” was thought to be a different species, but it is now considered to be identical to austinite. Named in honour of Professor Austin Flint Rogers (1877–1957), American mineralogist from Stanford University, California, USA.


Any crystal which has a mirror plane as one of its symmetry elements has the property that its mirror image (with any plane as the mirror plane) can always be superimposed on the original crystal by translation or rotation or both.
If there are no mirror planes as symmetry elements then the mirror image of a crystal cannot be brought into superposition with the original crystal by rotation or translation. This is enantiomorphism, and the mirror images are said to be enantiomorphs of each other.
The possibility of enantiomorphic crystals is determined by the crystal symmetry, ie by the point group of the crystal species. There are 32 possible point groups, and 22 of these are capable of forming enantiomorphs. The enantiomorphs are designated right or left handed, according to whether they rotate the plane of polarised light to the right or to the left. Sometimes it is clear from the outward form of the crystal whether it is right or left handed, and sometimes optical methods are needed to determine this.
The commonest enantiomorphic mineral is quartz, with point group 32; all quartz crystals will be either right or left handed, but it may not be possible to distinguish this from the external form unless some critical crystal faces are present.
Austinite has point group 222, with no mirror planes, so austinite is also an enantiomorphic mineral, occurring as both right handed and left handed crystals, with right handed ones more common.


Austinite is a rare mineral in the oxidation zone of arsenic bearing base metal deposits, where it is found developed on the colloform (pertaining to the rounded, globular texture of mineral formed by colloidal precipitation) surface of limonite or lining small cavities. It is closely associated with adamite, and appears to be a later mineral.
Associations: Adamite, quartz, talmessite and limonite at the type locality.
Type Locality: Gold Hill Mine (Western Utah Mine), Gold Hill, Gold Hill District (Clifton District), Deep Creek Mts, Tooele County, Utah, USA.

Gold Hill is located south of Wendover and west of the Great Salt Lake Desert. Go south out of Wendover and follow the signs to Gold Hill.

40°9’38″N – 113°48’20″W

Magnet Cove Arkansas – Rockhounding

Filed under: regular postings — Gary @ 9:44 pm


Magnet Cove! The most mineralized 5 square miles in Arkansas!

History of Collecting
Before 1820, locals recognized there was something different about this area. Their compasses went haywire as they walked across the ground. Then by the 1840′s people began to notice a variety of unusual minerals. Later in the 1850′s many specimens had been shipped to Europe and examined by German mineralogists and Magnet Cove’s fame as a collecting area began.

Hot Spring County
Magnet Cove Historical Marker

“This is Magnet Cove which covers an area of irregularly oval shape about five square miles. The cove is made up of volcanic rocks which have gradually been forced to the surface of the earth. It was probably not an eruptive volcano. About 42 distinct mineral species have been found in the cove and many of the mineral types and combinations are of world-wide interest to mineralogists because they are know to occur in only two other localities, the Ural Mountains and the Tyrolean Alps. Here was the home of James Sevier Conway from 1834 until after 1840. Here the eminent English geologist G.W. Featherstonhaugh visited in the autumn of 1834.”

Truly a world-famous site
Magnet Cove has provided many heydays for rockhounds, collectors, mineralogists, and geologists. And it continues to do so when access to sites is available. There are 2 comprehensive publications on Magnet Cove. The earliest is a part of the Arkansas Geological Survey’s Annual Report for 1890 – “The igneous rocks of Arkansas” by J. Francis Williams and the most recent is USGS Professional Paper 425 (1963) by Erickson and Blade. Both of these reports are long out-of-print, but may be reviewed at major university libraries. William’s report goes into some detail concerning the minerals and their occurrence at Magnet Cove and the USGS report details the chemistry, along with some additional mineralogy, of the igneous rocks. Many of the sites named are the same, despite the decades of time separating these two publications. There have also been a series of articles in recent years in
Rocks and Minerals magazine on various minerals and sites of this area.

<read more here>

Illinois Rockhounding

Filed under: Rockhound Travel — Gary @ 9:24 pm



Mazon Creek fossil beds

The Mazon Creek fossils are conservation lagerstätten found near Morris, in Grundy County, Illinois. The fossils are found in ironstone concretions, formed approximately 300 mya in the mid-Pennsylvanian Epoch of the Carboniferous Period. These concretions frequently preserve both hard and soft tissues of animal and plant materials, as well as many soft-bodied organisms that do not normally fossilize. The quality, quantity and diversity of fossils in the area, known since the mid-nineteenth century, make the Mazon Creek lagerstätten important to paleontologists, in attempting to reconstruct the paleoecology of the sites. The locality was declared a National Historic Landmark in 1997.




The Mazon Creek fossils are found in the Upper Carboniferous Francis Creek Shale; the type locality is the Mazon River (or Mazon Creek), a tributary of the Illinois River near Morris, Grundy County, Illinois. The 25 to 30 meters of shale were formed approximately 300 mya, during the Pennsylvanian period. The fossiliferous concretions are usually found within the thickest deposits of Francis Creek. The concretions occur in localized deposits within the silty to sandy mudstones, in the lower four metres of the formation. The paleoecosystem is believed to be a large river delta system, deposited by at least one major river system flowing from the northeast. The sediments are believed to derive from the Appalachian orogeny events. The delta had a tropical climate, a result of the area being within 10° north latitude of the equator during the Pennsylvanian.

The remains of plants and animals were rapidly buried by the sediment deposited in the deltaic system. Bacterial decomposition of the remains produced carbon dioxide that combined with dissolved iron from the groundwater. This process formed siderite in the sediments surrounding the remains, forming detailed casts of their structure. Lithification of the sediments formed protective nodules of ironstone around the now fossilized remains.

Rhizodus scale

Rhizodus scale

The fossiliferous concretions are found in the Mazon River area of Grundy, Will, Kankakee, and Livingston counties. Additional fossils are found in LaSalle County, Illinois; between the Vermilion River and Marseilles, Illinois. The ironstone concretions are recovered from exposures along streams, roadcuts and in active or abandoned coal mine areas.

The site’s importance was realized in the mid-nineteenth century: “the nodules of Mazon Creek, where fragments of plants, even of the softest texture, have been preserved in their integrity”.


The Mazon Creek flora comprises over 400 species from at least 130 genera. However, the true number of species is difficult to determine. Paleobotanists name separate plant structures with different names by convention, inflating the number of fossil plant taxa. Paleobotanists are currently determining which taxa are valid.

Mazon Creek flora includes: lycopsids, related to modern club moss, with arborescent forms named Lepidophloios, Sigillaria and Lepidodendron, and herbaceous forms called Lycopodites and Cormophyton; sphenopsids like Calamites a tree-like horsetail relative, with common foliage names of Annularia and Asterophyllites, and a vine-like form called Sphenophyllum; Pteridophyta as marattialean tree ferns and Filicales and Zygopteridales understory ferns, with common foliage names of Pecopteris, Acitheca and Lobatopteris; pteridosperms, also known as seed ferns, an extinct group of plants that grew both as trees and smaller shrubs, with features like pinnated leafs similar to true ferns, but reproduced by seeds instead of spores; they had common foliage names Mariopteris, Alethopteris, Odontopteris, Neuropteris, Laveineopteris and Macroneuropteris; extinct Gymnosperm Cordaites, believed to be closely related to and sharing many features with modern conifers.


The Mazon Creek fauna has over 320 species of animals that have been identified. The fauna is divided into two components: the marine Essex fauna and the land and freshwater Braidwood fauna, that were washed into the deltaic sediments. The Essex fauna includes jellyfish, sea worms, snails, saltwater clams, shrimp, sea scorpions, cephalopods and fish. The Braidwood fauna includes insects, millipedes, centipedes, scorpions, spiders, other arachnids, amphibians, freshwater fish, freshwater shrimps, freshwater horseshoe crabs and ostracods. The oldest known beetle has been described from the Braidwood fauna.

The most famous faunal member is Illinois’ state fossil Tullimonstrum, known popularly as the Tully Monster.

The Tullimonster is placed in its own phylum and is unique to the period. Johnson and Richardson (1956) describe the Tullimonster as being a marine, carnivorous, worm-like creature closely associated with the jellyfish and having a soft body with no internal skeleton. It is hypothesized that storms blew seawater and sea organisms further inland than they would naturally occur, thus the Tullimonster and other marine organisms were introduced inland where they were buried and fossilized. This allowed researchers today to study these organisms that would normally not be preserved. Evidence of marine forms of life is also suggested by the fossilized clam trails and burrow mottles. Other marine animals that can only be found in the fossil record from Mazon Creek are hagfish and lampreys.