Tag Archives: fossils
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.
Okay, so I didn’t know this was a thing, but I found out there is a National Fossil DayTM here in the States. It’s the Wednesday of Earth Science Week in October.
Now that is my kind of holiday. The idea behind it is to show how much we can learn about the past (and possibly predict about the future) from fossils and the need to understand and preserve them.
The National Park Service has some great art and articles as well as a list of related events-check to see if there’s anything going on in your area!
I was reviewing a children’s nonfiction graphic novel on dinosaurs-First Second Press’s Science Comics (love the concept!) Dinosaurs: Fossils and Feathers. It was more about the discovery and scientists than dinosaurs themselves. There were some aspects of the book that I liked, some I wasn’t so fond of.
One thing that did catch my eye was the name Mignon Talbot. They mentioned that she was the first woman to name a dinosaur. I hadn’t heard of her before. So of course I had to hunt down a little more information. She was a professor of Geology and Geography at Mount Holyoke College for thirty-one years in the early 20th century.
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.
-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.
Turritella agate is the youngest fossil I currently use. The shells inside it belong to creatures who emerged millions of years after the ammonites went extinct.
I hadn’t realized that Turritella agate was a misnomer. (It took me long enough to catch the name. I was told it once briefly and it sounded to me like tarantula or tarantella…)
Apparently it was originally named after a species of saltwater snail that has a similar steeply pitched shell to the ones found in this stone. Sea snails of the genus Turritella had been previously found fossilized in agate in California and Texas. Most stones called turritella agate come from Wyoming, Colorado and Utah, which have freshwater deposits.
The fossil deposits range from sandstone to much chalcedony. (Agate is a type of chalcedony, so that part of the name gets partial credit for accuracy…) They bear large quantities of fossilized freshwater snail shells from the genus Elimia. A once flourishing species now extinct, they date from the Eocene. The beds are estimated to have been laid down 51-46 million years ago in what was then a series of shallow lakes.
They lived well after the dinosaurs died out, in a warm world where small mammals were establishing a foothold. The overbearing greenhouse gases and hot temperatures in a world almost without ice are thought to have favored small mammals more able to cope with heat, as well as reptiles.
I confess I keep having to google it in order to remember how to spell it. I really need to remember, especially since every time I do I find more sites ascribing metaphysical properties to it. That always gets me a bit cranky. I just don’t get why it can’t be awesome because it’s a slice of life from a long lost world-one with different continents and weather and creatures. How is that not cool enough?
I saw one of my coworkers had a Saint-Saens CD and she let me borrow it. I remember dancing (using the word very loosely) to the ancient record of it my parents had when I was a little girl. I didn’t realize or remember that one of the movements was called fossils.
Apparently Ogden Nash was hired to write a series of short poems to go along with the movements. Some of them are pretty bad/badly dated. But the introduction one is excellent and I very much like the images of his fossils poem!
by Ogden Nash
At midnight in the museum hall
The fossils gathered for a ball
There were no drums or saxophones,
But just the clatter of their bones,
A rolling, rattling, carefree circus
Of mammoth polkas and mazurkas.
Pterodactyls and brontosauruses
Sang ghostly prehistoric choruses.
Amid the mastodontic wassail
I caught the eye of one small fossil.
“Cheer up, sad world,” he said, and winked-
“It’s kind of fun to be extinct.”
Along the fossils theme–I visited the Page Museum at the La Brea Tar Pits weekend before last. Had a few hours to kill before a family wedding so decided to go take a look despite everyone saying it was just a pit and not worth it.
Apparently they didn’t notice the museum you have to walk around to see said tar pits and not a one went in… It’s a nice little museum, I went in and goggled at the fossils they’ve found in the pits. They range from the huge Columbian Mammoth they have on display to the teeny mouse toes in their Fishbowl Lab to the vast quantity of dire wolf skulls on the wall…yes, dire wolves were real creatures and weren’t invented for fantasy novels….
Basically the tar pit is just that-natural asphalt. Animals would get stuck to the tar, and not all would be able to escape. Those that got stuck would attract predators and scavengers, and some of those would also get trapped. So it’s a whole ecosystem of life, predation and death from 11,000 to 50,000 years ago preserved in a smelly sticky mess! (How the La Brea Tar Pits Work for more details.)
I didn’t have enough time to take one of the tours, so I can’t vouch for those. But the atrium was lovely, and the displays were very nicely done. They have some assemblages of bird fossils and then a painting of what it might have looked like right behind it in the display case.
A short photo essay I found on the museum. (Their photos turned out better than mine!)
(Okay, the animatronic mammoth is seriously dated besides being the wrong species, but kids seemed to love it.)
So if you’re in the area and up for braving the insanity of traffic in LA, stop by and go inside. Take time to walk through the park too.