Clams with Calcite
While browsing the Arizona Mineral and Fossil Show InnSuties at 475 North Granada, I was delighted to discover several displays of fossilized clams with calcite offered by Pat Curry of Nature's Creations in room 429. The clams were interspersed on his tables and shelves with agatized corals that were also high on eye candy factor. These are Mercinaria clams which lived approximately 4 million years ago in what is now present day Okeechobee County, Florida. Now I generally tend more towards the ammonites when it comes to appreciating fossil shells, but the aesthetic and unique combination of fossil and mineral crystal presented by these Mercinaria/calcites is outstanding and slammed needle of my cool factor detector on sight. These want from $100 to $175 to go home and I considered them a great value relative to the overall presence and effect. Of course these are your basic must-have for any calcite collector who is also into fossils...
Presented here are several that I considered to be among the creme of the collection. Pictured above left is matrix piece I thought quite fine. It is about 8" overall and the clam is about 3.5 inches across. This one wants $150. Above right and below left and right are three similar sized clams which were more or less free of matrix. These each wanted in the range of $110-$130 to go home.
Depicted above is my choice for the creme de la creme of the clams with calcite. This aesthetic matrix piece is about 8 inches overall. This piece featured the largest calcite crystals by far, with a nice cluster that is about half the length of the shell. Of course this piece was commanding a little more clams of the folding variety than the others, wanting $175 to change shelves.
I consider the matrix on this one and several of the other clams to add considerably to them as specimens and display pieces. During the course of our conversation, Pat remarked that he personally agreed regarding the matrix pieces but that some buyers had definitely preferred the more or less matrix clean pieces. Now I have a hard time comprehending the why of that. Not only does the matrix carry intrinsic information about the fossil and the environment it formed in, the matrix on these clams also provides some excellent contrast in both tone and texture for these pieces when you appreciate them in compositional terms. I also note that you can trim the matrix to produce very effective self-contained stands on many matrix pieces without adversely impacting them as specimens.
In addition to fossil clams and agatized coral, Pat is showing a nice selection of collectible shells. I wonder if preferring their clams with calcite sans matrix could be more of a shell collector mind set and thing.
I do have a collection of shells from the Sea of Cortez acquired while on various diving trips and expeditions there. The preparation to display them in as pristine and beautiful condition as possible did entail considerable bother and work with a dental type pick and soaks in a weak acidic solution to clean and relieve some of the older ones of encrusting crud.
Pat showed a number of effective and affordable conversation starters and display pieces for those sharing a general interest in the naturalia of inner space. Depicted above is a skeleton of Euplectella, commonly known as the Venus flower basket sponge. Pat is offering these at $10. The Venus flower basket is a type of tropical, deep-water sponge with skeletons composed of spicules of silica and is a member of Hexactinellida, the "glass sponges". They are deep water creatures typically found at depths of 1,500 to 15,000 feet in the Western Pacific.
In Japanese culture the Venus flower basket serves as a traditional symbol of marriage and unity. The closed cylinder provides a home to a pair of shrimp which enter their unique bridal chamber while tiny. As they mature and grow in size the crustacean couple become encased within the sponge for the duration of their lives. Their offspring escape home while in the embryo stage and develop in the open sea to begin the search anew for a mate and a bridal chamber of their own.
Glass sponges are unique in having evolved silica as opposed to calcium skeletons. Sponges were regarded as plants until 1765 when internal water currents were first observed and studied in them whereupon sponges were recognized to be filter feeding animals. Sponges can actually survive being mashed through a sieve - the constituent cells "know" how to reassemble the organism on the other side. Now there's a capability us "higher" animals just can't match, although I suppose a case can be argued that we don't need to, due to having brains that resist being mashed through a sieve in the first place... In comparison the level of organization of sponges is very simple as animals go, as they have no definite organs and no definable nervous systems. Yet they carry on all the functions necessary to animal life and have done so very successfully for many millions of years.
Glass sponges extract silicon dioxide from sea water as a source of silica to form the skeletal matrices of their bodies. The silica spicules are typically arranged in a hexactine lattice of six points or some multiple thereof. The cylindrical skeletons of the Venus flower basket have the appearance of spun glass. During a scientific conference in San Francisco, Bell Labs research scientist Joanna Aizenberg found a Venus flower basket while browsing in curio shops for shells and other marine objects. Aizenberg was exploring an interest in bio-mimetics, where scientists study how biological systems are "engineered" and how they might adapt and apply nature's handiwork to human technologies. Upon examining the Venus flower basket's silica fibers Aizenberg and other researchers discovered they transmit light. "It's possible that the whole sponge acts as a fiber-optic lamp," Aizenberg says.
The sponge adds a layer of tough and flexible organic material onto its glass fibers. This organic layer limits cracks in sponge fibers, which is a weakness of the man-made versions. Research is currently underway to learn more about how these sponges are able to manufacture optical fibers at low temperatures, and how to adapt analogous structures in man-made optical fibers to improve their toughness and durability.
So now this most "lowly" of the animals incorporates a naturally evolved optical fiber system. One can not help but marvel at what other amazing discoveries regarding even the most "simple" things must surely await us. What can possibly be next?
These fossils registered high on my cool meter even before I knew what I was looking at. At first I assumed these to be some type of brittle star, as I have observed extant stars while diving the Sea of Cortez similar in appearance and size. However upon inquiring I learned these are Saccocoma pectinata, a free swimming Jurassic crinoid from the Solnhofen Limestone deposits near Bavaria, Germany. The double in hand above right spanned about 4.5 inches overall. The singles wanted $35 and the doubles wanted $55 to drift your way.
This locality is famous for remarkably preserved fossils due to special conditions that developed there near the end of Jurassic time. About 155 million years ago, a shallow sea studded with islands covered much of present day Germany. Sponges and corals formed reefs that eventually divided parts of the sea into separate lagoons. The salinity of these warm, isolated lagoons rose substantially and apart from cyanobacteria and protists, nothing could survive for long in the anoxic bottom waters of the lagoons. However, flora and fauna that fell into or was washed into these lagoons were buried in soft carbonate muds. The remains of many delicate creatures were thus undisturbed by scavengers or dispersed by currents and became fossilized with remarkable preservation of detail in the Solnhofen Limestone. Archaeopteryx, one of the most significant and famous fossils ever discovered, is from the Solnhofen Limestone.
You could take your pick of both prepared and unprepared crinoid specimens. Now I consider it a given that you can safely assume just about any fossil sitting out atop table at Tucson has undergone some degree of preparation. It's just a matter of extent. The specimens depicted above left and right serve to illustrate the difference between one of these crinoids that's undergone a minimal preparation and one that's been a little further enhanced.
Jim is also showing a nice collection of Florida agatized coral. This material is from the Withlacoochee River bed and dates from the Oligocene. I noted prices on these specimens ranging from $26 to $450, most of which were offered as matched pairs. They originated as ordinary coral, which is the limy exoskeleton of colonial marine animals. While alive coral polyps combine lime from sea water with carbon dioxide excretions to form their exoskeletons, which aggregate to form coral reefs. Coral reefs provide critical habitat for marine life and can reach immense proportions. The Great Barrier Reef of Australia is approximately 2011 km in length and 72 km across at its widest point and is known to harbor approximately 400 species of coral, 1,500 species of fish and 4,000 species of mollusc.
This agatized coral formed as silica present in water replaced the limy coral skeletons with chalcedony. The process is believed to have taken place over the course of 20 to 30 million years, the end result being a pseudomorph, where one mineral becomes replaced another with the shape of the original material preserved. Three primary localities for agatized coral in Florida are Tampa Bay, the Econfina River, and the Withlacoochee/Suwannee River beds.
The color of agatized corals can be truly stunning. I can't think of any other source of chalcedony that provides a more marvelous riot of color than agatized coral, and it is color that is no doubt the driving force behind the desirability and popularity of agatized coral as a collectable material. The matched pair depicted above wanted $26.
The matched pair above was about 6 inches across and wants $150.
The unpaired piece pictured above was about 11 inches across and wants $300. This one is fine to my eye. The way the chalcedony is crystallized in this specimen is very similar in effect to some upscale chalcedonies from the zeolite producing regions of the Deccan Traps in India, of which I am also covetous.
As is the norm for Tucson, the best of Jim's corals were going fast. Detailed at left and below is my pick for the top agatized coral pair shown by Jim that was still available at the time of my visit. Each half is about 12 inches overall and both are distinctive pieces with special attractions of their own. This pair wants $450 to change shelves.
Pretty colors huh?
Fossil fish specimens from the Green River Formation are ubiquitous at Tucson. But you'll see literally thousands of specimens of the more commonly recovered species such as the herrings Knightia and Diplomystus to every gar. So this Lepisosteus simplex shown by Lindgren Fossils in Room 181 at the Arizona Mineral and Fossil Show InnSuites just cried out to me for a picture and I was pleased at the opportunity to oblige it.
The Green River Formation is extensive, covering approximately 25,000 square miles of Wyoming, Utah and Colorado. Green River time spanned approximately 10 million years from 40 to 50 million years ago during the Eocene Epoch of the Cenozoic Era. This formation is one of the largest lacustrine (lake sediment) formations known and is composed of deposits from three principle lakes. Fossil lake, centered in Southwest Wyoming, was the smallest and dates from the early Eocene. Lake Gosiute deposits span the Lower to Middle Eocene. The largest deposit from Lake Uinta ranging across the Utah-Colorado border spans most of the Eocene Epoch.
The excellent preservation of Green River fish fossils is attributed to the great depth of the lakes and cold, anoxic conditions which would have slowed the process of decomposition and prevented scavengers from disturbing the carcasses.
This gar is approximately 25" overall, which is an average length for the species.
Depicted above are scale and fin detail from the gar.
Fossils by Anthony Lindgren Room 181 at the Arizona Mineral and Fossil Show InnSuites - PO Box 36, Frontier, Wyoming 83121 Phone: (307) 877-3145 Email: firstname.lastname@example.org
Tynsky's Fossil Fish, Inc. Room 107 at the InnSuites Show - 201 Beryl Street, Kemmerer, Wyoming 83101 Phone: (307) 887-6885 Email: email@example.com