Tag Archives: fossil

Split ammonite fossil earrings in 14K gold fill.

Split ammonite fossil earrings in 14K gold fill.

Since today is National Fossil DayTM, I wanted to do a bit of a show-and-tell. I love working with fossils in my jewelry, and a number of them have ended up on here, so I thought I’d do a brief overview of the ones I use most often

 

Fossils are fascinating. Just think for a minute about the intricacy of ancient life that they preserve. They’re like little time capsules.

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Jurassic Reliquary

 

This is a piece of agazitzed dinosaur bone inlaid with ammolite that I wrapped in 14K gold fill. I couldn't resist this striking combination of fossils.

This is a piece of agazitzed dinosaur bone inlaid with ammolite that I wrapped in 14K gold fill. I couldn’t resist this striking combination of fossils.

Agatized dinosaur bone is sort of like meteorite, it’s awesome just BECAUSE.

 

If you look at a cross section of a bone you’ll see holes. These are the places that used to house blood vessels and bone marrow.

 

Gem bone dealers call these spaces cells. And they are, in the sense of small enclosed places. What they are not is cells in the biological definition that involves nuclear material surrounded by a membrane or wall. Here we’re talking about seeing the larger structures formed by the bone cells.

 

Agatized dinosaur bone is the result of these empty places being replaced with mineral materials. The most common of these is chalcedony. Transparent chalcedony with patterns or banding is called agate, so dinosaur bones replaced with chalcedony are called agatized dinosaur bone, dino bone, or gem bone.

 

The largest gem bone deposits are in Utah and Colorado from the late Jurassic Morrison Formation. It is around 200-150 million years old and formed from silt and sand from flood plains.

 

There are a lot of variables to evaluating gem bone! There’s also a lot of division between what specimen collectors and jewelers will be looking for.

 

-Color. The brighter the better. Neutral colors are less in demand for collectors, though they work well for jewelers. Black is the most desirable for the cell outlines, followed by white, since both will give a dramatic contrast.

 

-Intensity. Again, the most intense, rich colors are generally the most in demand. Pastel colors are rare, so some prefer them. (I myself really like the hard to find delicate baby blue color.)

 

-Number of Colors. Apparently seven colors in one fossil is the least found and the most prized. I’ve never seen one like that in real life.

 

-Durability. Chalcedony is a fairly hard stone. Some of the other minerals found in gem bone-opal and calcite-are much softer, but calcite is supposed to improve the brightness of color and give the surface of the stone a silvery sheen. So again it depends on what it’ll be used for-a display piece needs less durability than a ring inlay.

 

-Cell Size. Generally the larger the better, so long as the contrast is good.

 

-Cell Pattern. There is a very rare fanning pattern only found in the vertebrae of some species, it’s generally a collectors only item since it’s considered too rare to cut up for jewelry.

 

-Type of Bone. For collectors the vertebrae with their unusual patterns, especially if they’re part of a pair. The ends of large bones are valued by both collectors and jewelers because they’re more likely to have large and well defined cells.

 

-Completeness of Bone. Again, for collectors. Complete bones are more valuable.

 

 

This would be a really awesome fortification with amethyst crystals. From the Smithsonian.

-Presence of Agate Fortifications. They sound to me like particularly beautiful castles, but apparently this is the proper term for the little crystal surprises you sometimes find in the bone. Sometimes fractures or large cells are filled with patterned agate, very rarely even amethyst or citrine crystals. Again, the larger and more unusual the better. I’ve only seen tiny white crystals in person.

 

-Treatment. Most of the agatized  dinosaur bone in jewelry isn’t treated beyond the cutting and polishing. Sometimes cracks or holes will be filled with epoxy. Collector specimens require more treatment to stabilize them, since it’s a matter of keeping a whole piece rather than selecting the best part.

 

Most of the agatized dinosaur bone I’ve worked with is at the cut an polished level, but the bones inlaid with ammolite mosaic do have a coating. Ammolite is very thin and is often coated to give it a layer of protection. With these inlaid pieces the bone has been given the same coating as the ammolite so they have the same kind of sheen and look more of a piece.

 

Agatized dinosaur bone is pretty sturdy. But it’s still very old and best treated with care. It’s not a good idea to keep it in places that will get extremes of heat or cold-like a display case facing a window, wearing it into a sauna-or worse, a place that will go from one extreme to the other-like a car. It’s also best to remove any jewelry before swimming, chlorine compounds can bleach the ancient colors.

 

So they take a little extra care, like plenty of other fossils, but it’s DINOSAUR.

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Fossil Monochrome

orthoceras

 

straight horned fusillade,

storm of black and white bullets

shot through ancient seas

racing head and foot into

eternity’s sediments

 

Orthoceras are ancient mollusks. They first emerged nearly 500 million years ago and went extinct nearly 200 million years ago. (They existed from the Ordovician through the Triassic. They had a 200 million year overlap with their younger cephalopod cousins, the ammonites.)

 

Imagining orthoceras alive.

 

Their name is descriptive, it means straight horn. They were soft bodied creatures that lived in the newest segment of the shell. Periodically they would grow a separating wall called a septa and close off the too small part of the shell. The different composition of septa and the external shell allowed them to fossilize differently, so we can still see their shapes today. (The curved lines running perpendicular to the outline of the fossil.)

 

The long channel you can see running along the center of the fossil-two parallel thin dark lines-was a hole that housed a strand of tissue called the siphuncle. It was (and is in nautiluses today) a way for them to filter water in and out of closed chambers, controlling buoyancy.

 

They probably worked in a similar fashion to those of creatures living today. It’s a pretty interesting method of control. It isn’t a muscular thing like you’d imagine. Instead it works by osmosis. Basically the change was controlled by blood salinity. Water would move from areas of lower salinity to higher in an attempt to achieve an equilibrium. Gases dissolved in the blood would slowly fill the chambers as the water moved elsewhere.

 

Despite the likelihood of this passive method of control, some propose that this might also have aided in propulsion.

 

Since all of orthoceras relatives were/are predators, it is fair to guess that they were as well.

 

Their fossils are often found in assemblages-like sheets of them mostly parallel-the only species present. It looks like an Edward Gorey inspired repeating wallpaper pattern! You see beautiful displays of them in museums or at fossil shows. (I’ve also seen really cool things made out of them, including the best bathroom sink ever!) Interestingly these groupings are found mostly amongst the older of the fossils.

 

Scientists aren’t sure why this is. Some believe it is evidence of post mating mass deaths, others that they simply traveled in schools. It’s been suggested that they are aligned so nicely because they shifted after death due to currents over the ocean floor.

 Minimalist Monochrome Orthoceras Pendant

I’m fascinated by the elegant simplicity of orthoceras fossils. They’re often black and gray and the smooth bullet like shape is a lot of fun to work with. It suits a lot of different styles. In my most recent turn with them I used three different colors of wire to try to mimic the tones and striped effect of the chambers in a simple woven frame.

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An Ammonite Again!

A whole ammonite this time, chambers well hidden but polished to show off the wonderful iridescence these guys sometimes have.

I posted another ammonite, so decided I might as well share another of my fossil tanka. Because sometimes you just have to write on an improbable prompt to keep from going mad from boredom (or frustration) at work!

 

ammonite

 

frozen whirlpool, still

expanding, trying to flee

the growing chambers’

sutures–inescapable

rooting in the stony past

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