Pearl

[falcondriver]

Is this a pearl?

FD

[Uncle Siphuncle]

FD

Depends where it was found. From pictures I can't tell a Kamp Ranch pearl from 000 buckshot personally.

[falcondriver]

Not very good with the formations but It was found in Mansfield TX in an area of verts and teeth. Someone will post the formation soon, many people have been in this location.

FD

[Uncle Siphuncle]

If it came from a yellow marly lithology it is probably Lower Britton. I believe that the Kamp Ranch would lie a little to the east of Mansfield if it even extends that far south of Dallas. Are there lots of oysters at the exposure you collected? On the few hunts in the Kbrl that I've done I didn't take notice of the oysters as I was focused on vert material. I didn't see any ammonites in it either. The Kamp Ranch is a harder limestone with Prionocyclus ammonite impressions near the top. The limestone is somewhat of an oyster hash studded with shark teeth as well as occasional reptile material and of course, pearls if you are lucky. I would think if it was buckshot you'd notice extreme density compared to a pearl or even a rock the same size. I've been briefly tricked before by lead shot when hunting for pycnodont teeth or pyritized micromorphic ammonites in areas where people have discharged shotguns.

[Guest N.AL.hunter]

I wonder if there is a uniform density for fossil pearls so that a specific gravity test could be done?

[Auspex]

It sure looks like a pearl, and a big one at that!

Drop it into a glass of vinegar; if it dissolves, it was a pearl

(I'm voting for pearl; it seems to have layers. Purty durn nice!)

[jax]

I think that formation is maybe britton shale... Lance would know better than I would

That looks like a pearl, when did you find it??

This is the one I showed you the other day.

Heres the others I have:

http://www.thefossilforum.com/index.php?sh...71&hl=pearl

Next time im out that way I'll take a look at it. But it looks good

[LanceH]

Below the Kamp Ranch layer it's called Britton shale and above the Kamp Ranch layer it's called Arcadia Park shale. They are all part of the Eagle Ford formation (some say group).

Most of the Britton I have seen is yellowish soft shale (melts when wetted). Most of the weathered Arcadia Park I have seen is also yellowish shale/clay. I have noticed that some of the Arcadia Park (upper most?) is a hard blue-gray clay (weathers to the yellow soft stuff?) in fresh exposures and creek beds.

I've also noticed there maybe other minor Kamp Ranch (flaggy) like layers in the Kef. Anyone else observe this? I've seen one definite Kamp Ranch outcrop within shooting distance of the Kef-Kau contact BUT have also seen a Kamp Ranch-like layer 2+ miles from the Kef-Kau contact.

[Roz]

Have never found one YET (I'm hoping), but it looks

like the fossil pearls that Jax has found and posted on here.

Doesn't look like metal to me at all.

[falcondriver]

There is a large deposit of oysters within walking distance and Jax has found some pearls in this location. Guess I need to take a walk tomorrow.

FD

[Mike Owens]

Looks just like the ones I found on the Trinity River. They are found in Inoceramus clam beds.

[Uncle Siphuncle]

I've heard some discrepancy between collectors in the DFW area concerning Kef stratigraphy. Some tend to call all hard limestone benches Kamp Ranch while others assert that some are limestone stringers in the Arcadia Park while others are Kamp Ranch.both holding similar shark tooth fauna. I haven't done much reading or field work on the subject, so hopefully an area expert can shed some light on this. The Arcadia Park limestone that I've seen personally outcropped in the shale as nodules with cool nacreous ammonites in some of them.

Here is another interesting side discussion - I've always assumed that pearls only grew in oysters. Can they form in other bivalves (clams) as well?

[Auspex]

Here is another interesting side discussion - I've always assumed that pearls only grew in oysters. Can they form in other bivalves (clams) as well?

There are fresh-water pearls, which would not be from oysters.

Paraphrasing Wikipedia:

"Nacreous pearls can form in the mantles of salt water oysters and fresh water mussels. Just about any shelled mollusk can form non-nacreous 'calcareous concretions', composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers."

Since the nacre (mother of pearl) is not distinguishable once fossilized, I suppose it is possible that these fossil pearls could come from clams.

[Maryland Mike]

I wonder if there is a uniform density for fossil pearls so that a specific gravity test could be done?

I suspect there would be a fairly uniform density for buckshot, so a specific gravity test ought to be able to confirm buckshot or not, don't you think.

[Guest N.AL.hunter]

Now see there... all i could think about was the SG of the pearl, but as Mike points out, shot mostly is from known metals like lead or steel... and thus eliminating those SGs could rule them out.

[jax]

Looks just like the ones I found on the Trinity River. They are found in Inoceramus clam beds.

I actually found a pyritized Incoceramus clam, shell is mother of pearl. These are claimed to have the pearls in them, and I have thought very hard about trying to split it open to see whats inside.

Mike, whenever your ready lets hit the Trinity river.

[Mike Owens]

Soon as it cools down a bit.

P.S. Remind me to show you a copy of a letter from the Smithsonian, (Erle G. Kauffman), that states "the pearls likely come from Inoceramus." "the host was very likely Inocermus cuvieri (Sowerby) or possibly Mytiloides of the M. labiatus (Schlotheim) group." He also states that he has one that is 6" in diameter! Now that's a BIG pearl!

[Uncle Siphuncle]

Looks like I learned something new today. In my mind I've only associated pearls with oysters up to this point.

As for the buckshot theory, sort of far fetched if it was found around oysters and/or Inoceramus, could also be confirmed based on size. Buckshot comes in discrete sizes as follows:

000 .350 inch dia

00 .330

0 .320

#1 .300

#2 .270

#3 .250

#4 .240

I would think that tolerance on diameter would be +/-.005 at most, otherwise you'd potentially have overlap of the sizes that are .010 apart in diameter. So not knowing manufactured tolerance and supposing my tolerance assumption is true, and also assuming that spherecity was not compromised on impact if it is buckshot, if your specimen is not extremely close to one of the diameters mentioned above, it can't be buckshot.

[tracer]

It's a pearl. FIrst of all, the "skin" is somewhat translucent and looks like fossilized nacre. Secondly, as Auspex said, where the outer layer is damaged, the surface underneath also retains the rounded shape, meaning it was laid down in layers. Thirdly, the undamaged portion, looking at the circumference, appears perfectly rounded, meaning it isn't a random nodule of something. It cannot possibly be a pellet of buckshot. First of all, lead either looks like lead or looks like oxidized lead, and the pearl doesn't look like either. Secondly, a surface layer doesn't crack off of a lead sphere - the lead would simply deform. It's a pearl.