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Malcolmt

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About a month ago I went to Penn with two fossil buddies and they both found prone greenops. Sadly I did not find one. However both of these greenops were split between the positive and negative and probably were missing some skin as the material was quite flaky. For one of my friends this was his first ever find of a prone greenops. Prone greenops that are nicely laid out are a very rare find in the Windom shale. Most of the ones I have found from there or others that I have prepped for people are fully, partially enrolled or distorted. So to my fossil buddy this was a bit of a special find. We wrapped up the two pieces in tin foil in the field and I agreed to take it with me and prep it for him. Well zoom ahead a month in time and I am going out with him last week to collect and he asks how is his greenops coming, whereby I realize that I have not only not started it ,but in my senility had forgotten I had it and had no clue where it was. Well when I got home it turns out that I had never unpacked the bucket of fossils from that trip and low and behold his fossil was packed just as we had left it. 

 

A careful look at both parts under the scope confirmed my opinion that the bug was in pretty rough shape , but a prone greenops, not to mention perhaps his first ever prone warranted we attempt to bring it back to life.

 

Unfortunately I did not take any pics until a ways into the prep but here is what I did to start. 

                       

1. Washed the mud off both plates scrubbing with a tooth brush

2. Squared up what would become the fossil plate with the diamond gas saw

3. Cut out as small as possible a square from the top piece of the matrix that contained the top part of the greenops using my 7 inch tile saw with diamond blade

4. On a belt sander using aluminum oxide 120 grit thinned the top piece as much as safely possible to help minimize my prep time later. 

5. Using super thin cyanoacrylate glue reattached the top portion to the main slab clamping tightly with a c-clamp.

 

Asusual all prep was done under a zoom scope at 10x to 20x magnification using a Comco abrasion unit and in this case a German Pferd MST 31 scribe exclusively.. Not a lot of scribing was done other than to outline the bug as the skin was not in great shape. Abrasion was pretty much done with a .18 and .10 nozzle using 40 micron previously used dolomite at 30 PSI.

 

Here is the bug after about an our of prepping . I have outlined in red where you can still see the outline of the section that was glued down. A lot of people do not realize that many of the fantastic trilobites you see on the market have actually been glued back together because the splits are often through the bug. I once did a Moroccan trilobite that was in 7 pieces when I received it

 

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Here is the bug after another 40 minutes

 

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Took some pictures of the prep but frankly they ended up too blurry to use so here is the prep after abrasion is complete and after I have repaired a lot of the parts that broke of in the split. I tend to use a white repair material and always take a picture to let the owner know what has been repaired

 

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Here is the bug after coloration applied . The repairs were allowed to cure overnight before coloration and a bit of extra carving to clean up spots.Just waiting for me to do a final cleanup tomorrow after everything has cured a bit more. A long way from being the worlds most pristine or perfect bug but I am relatively pleased that we were able to breath some new life into an ailing bug. Totally prep time about 3 1/2 hours over 4 days. I suspect the owner will be pleased with the result. I have seen people toss bugs in the field that were in this type of shape. For those of you who just need to know the bug is 27mm x 18 mm

 

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A slightly different view

 

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I'm sure your friend will be very happy with it!  You certainly made the most of what you were handed.

 

I hear a lot about this species of trilo or that species being found predominately enrolled or only in pieces.  The pieces I can understand given the stresses involved in turning sediment to stone, not to mention rock movement through the ages, etc.

 

But the enrolled part perplexes me.  I suppose whatever event buried them could have been foreseen and they all just had time to tuck it up (the human equivalent of putting your head between your legs and kissing your rear goodbye).  That would be a sight to see....millions of trilos on the ocean floor suddenly enrolling as they sensed some catastrophic event unfolding.   

 

Does anyone else have a take on why certain bugs are found predominately enrolled versus prone?

 

Everything is generated through your own will power ~ Ray Bradbury
 

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Walt, I have no scientific reason to believe this is true but I always convinced myself that rigor might cause muscles to contract after death and hence more are found enrolled than perfectly prone.

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I guess it could be similar to why some crustaceans, especially shrimp, curl up when cooked. Except maybe some other reason for the trilo.

If you're a fossil nut from Palos Verdes, San Pedro, Redondo Beach, or Torrance, feel free to shoot me a PM!

 

 

Mosasaurus_hoffmannii_skull_schematic.png

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1 minute ago, Malcolmt said:

Walt, I have no scientific reason to believe this is true but I always convinced myself that rigor might cause muscles to contract after death and hence more are found enrolled than perfectly prone.

Interesting.  I will have to check into that later.  Will post back if I find anything.... :)

Everything is generated through your own will power ~ Ray Bradbury
 

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Very interesting thread! :)

Thank you for sharing this, it's fascinating. 

I think it's likely that at least some of the trilobites that are found enrolled were trying to defend themselves at the time of death, buried in a flood of sediment, for example. 

I wonder if they enrolled when they felt ill?  

Life's Good!

Tortoise Friend.

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45 minutes ago, Walt said:

Interesting.  I will have to check into that later.  Will post back if I find anything.... :)

I have not yet found anything I can cite. 

Just an understanding from the literature I read that mentions trilobite fossilization that the event was sudden and overwhelming.  (landslide, volcanic ash event, etc).  My understanding of this is that death was instantaneous and the trilo was densely and completely engulfed.  This makes sense because the event had to seal off the specimen from the oxygen supply and predators.  I also get the feeling that a trilo buried in this type of event would not have much wiggle room to contract or relax after death.  

But as I said, I have found nothing to support this so your theory is as valid as mine.  More, given you experience collecting them.  :D

Everything is generated through your own will power ~ Ray Bradbury
 

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I'd have to double-check if it was in Levi-Setti's book, but there is a "death pose" for trilobites whereby the thorax looks concave, while the cephalon and pygidium point downwards -- this is something I see quite often among the Ordovician asaphids from Russia. In the case of PD bugs, a lot of the burial took place during sudden mudslides.

...How to Philosophize with a Hammer

 

 

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Kane..... I've crossed over to the dark side prepped two horn coral this afternoon... what is happening to me.... I definitely need to get out more.....

 

5b99664529bf4_horn1.thumb.jpg.4e95ff9fbf2c6e31a008c0c6301d3c09.jpg

 

Fooled Ya!!!!

 

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The horn coral just got in the way and were too risky to remove..

 

Actually I think they add to the overall effect of the piece...

 

But again not they are both enrolled and are not likely to be molts. They are 8mm and 6mm wide. Total prep time about 20 minutes. So was probably worth doing based on the result which looks quite nice. Fossil is as found no restoration, repairs or moving of bugs..... (Like I could do that in 20 minutes)

 

This season I have probably been finding 20 to 30 enrolled for every prone. Should take a census at the end of the collecting season. 

 

Horn 2.jpg

 

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Apart from commending you on such excellent work... what are you doing, man? Horn coral? Ah! :D 

 

It's a very nice association piece, for sure (but we still need to do something about getting you out more. :P ). I could see how removing the coral would have been a bit too risky for this one. I haven't touched many of my rollers yet and leaving those as a winter project... But I hope to find a whole lot more to keep the winter interesting. With rollers, I tend to remove them entirely from the matrix unless they are a multiple on the piece (like yours). 

...How to Philosophize with a Hammer

 

 

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What a lot of work! (but nice work as always)... I love that association piece. Nothing wrong with bonus fossils that give you a better sense of what their environment was like - and if I could have only one fossil from a given locality, I would choose something with more than one thing on it.

If you're not sick of prepping I should send you my little Widder Greenops that I received a while back in trade... It is smaller than that one and already mostly exposed - I think it would be one of those 20 minute deals.

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8 hours ago, Malcolmt said:

prepped two horn coral this afternoon.

Very nice.

If it was found this month or You have before pictures it would be a good candidate for FOTM.

Darwin said: " Man sprang from monkeys."

Will Rogers said: " Some of them didn't spring far enough."

 

My Fossil collection - My Mineral collection

My favorite thread on TFF.

 

 

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It was found last week and prepped this morning but I have refrained from submitting my own fossils to FOTM for the last year, though some I have prepped have made it there.

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5 hours ago, Wrangellian said:

What a lot of work! (but nice work as always)... I love that association piece. Nothing wrong with bonus fossils that give you a better sense of what their environment was like - and if I could have only one fossil from a given locality, I would choose something with more than one thing on it.

If you're not sick of prepping I should send you my little Widder Greenops that I received a while back in trade... It is smaller than that one and already mostly exposed - I think it would be one of those 20 minute deals.

Actually was not a lot of work ..... its quite a cute little piece actually sitting on the desk beside my computer right now. 

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You do some dang nice work Malcolmt.  I read "previously used dolomite" on your first post in this thread.  Ive always wondered about that.  do you screen it before reusing?

 

RB

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3 hours ago, RJB said:

You do some dang nice work Malcolmt.  I read "previously used dolomite" on your first post in this thread.  Ive always wondered about that.  do you screen it before reusing?

 

RB

Yes you must definitely  rescreen.

 

Here is a little bit on particle size / abrasion material 101

 

I have a complete set of  mining sieves in a stack going down to 325 mesh which is about 40 microns. (30,40,50,60,70,80, 100,120,170 200, 325) I also have a homemade ability to screen 500 and 600 mesh but rarely go that fine except for something extra ordinary. I throw anything that will not go through a 120 mesh sieve away. At 120 mesh a .018 nozzle will rarely get clogged but a .015 and especially a .010 nozzle will have issues clogging. My nozzle sizes are (.060. 040, .030, .025, .018, .015, .010 and some homemade ones that can go even smaller but just clog to quickly for general use.) I keep my sieved material in sealed containers and that tends to make them less prone to absorbing moisture.

 

If you can only afford a few screens the following is my recommendation (30, 120, 200, 325) You do not need the 40 through 80, the 30 catches the larger pieces and you throw away anything less than 120.

 

Over the years I have used the following abrasion materials, which have different hardness and densities

 

           sodium bicarbonate

           dolomite

           aluminum oxide

           silicon carbide (600 and 1200 mesh)

           nepheline syenite

            calcium carbonate

            magnesium carbonate

            aluminum hydroxide

            calcined alumina

            iron oxide

 

90% of my preparation is done with dolomite, with maybe 5% baking soda and the rest combinations mostly of either dolomite and silicon carbide or dolomite and aluminum oxide). For example I bought 500 grams of 600 mesh silicon carbide 2 years ago and I still have probably 250 grams left. (Very hard , very dense, lots of mass, super fine)

 

The more uniform the particle size the better your abrasion equipment is going to run. As material gets used the blocky sharp edges of the particles are rounded off and the abrasive cuts less and operates more on transmission of energy than cutting power. Except for Moroccan material my preference is to use recycled dolomite abrasive, it does not clog as much, the particle size is very uniform and it is much more forgiving. For Moroccan material I use new unused dolomite with up to 10% 600 mesh brown aluminum oxide added as needed. I first try dolomite on the Moroccan  matrix and if that works reasonably well then dolomite is all I use. aluminum oxide even 10% in dolomite is very unforgiving. It also will frost the glass on your blast box as the particles bounce up. Without aluminum oxide I change the glass in my blast box about every 3 months, with aluminum oxide in the dolomite about every 2 days.  (I rotate the glass half way through its life as the front part of my box gets more use than the back. 

 

For more delicate fossils that are very thin skinned I will use sodium bicarbonate that goes through my 325 mesh sieve. Almost all the box of good oldArm and Hammer is less than 325 but I find it needs to be dried in the oven at 225 F. for 30 minutes to not clog things up. I do not recycle the sodium bicarb as it is cheap and once used is not that good at cutting. I suspect the particles are damaged far more than the dolomite which is slightly harder on first use.  I do operate a dust cyclone in front of my hepa shop vac which removes about 97% of the abrasive before it hits the shop vac, extending the life of the vac. I get about 1 to 1/2 years out of a shop vac before the motor is toast but I likely run at least 20 hours a week , every week sometimes more.

 

I do not reuse the material that reaches the dust cyclone because I use the shop vac to clean up in the prep area which is a laundry room. Beside dolomite is cheap at about $25 Canadian for a 50 pound bag.  I only reuse the material in the blast box, which I empty about every other day. If a piece breaks off during prep you have to find it, so the more often you empty the box the less problem to find a missing piece. I always empty the box before starting a major piece.

 

A 50 pound bag of dolomite lasts me about 6 months with my recycling. I figure I reclaim about 80% of the material I use and about 20% ends up in the dust cyclone. My source for dolomite, which is used for pottery is a very uniform approximately 40 micron size. About 98% of the 50 pound bag is 44 microns or less and according to the suppler none is greater than about 100 in size. When I first started buying this material i screened some samples and pretty much confirmed that very little in the bag is less than 120 mesh and just about everything will pass through a 200 mesh. I had previously bought cheaper dolomite from other suppliers that was garbage...in one case about 40% of the bag was between 100 and 120 mesh. That was disappointing because I actually got it from a company that does blasting and deburring as a business. Apparently they are not that concerned about particle size, whereas pottery people are.

 

Particle size is of paramount important in getting good results. As a rule of thumb you should be using a particle size that is no larger than half the size of the smallest feature you are looking to preserve. If you have a groove that is 40 microns wide you can never clean it with particles that are 120 microns across. So why not use the smallest particle size say 1 micron. Well for some extremely delicate and fine fossils that may be the answer. But small uniformly sized particles of non toxic materials are extremely expensive as they generally are chemical precipitates. As particle size gets smaller particularly below 3 microns in size , hazard levels go through the roof and shop vac  hepa filters and drywall filters get much less effective. Also as particle sizes get smaller they have less mass. In the end your abrasion is a result of energy imparted which is a function of mass, velocity (PSI) and shape of the particle (rounded versus sharp edges)

 

Hope a bit of this information was useful in a rambling kind of way. IF you have specific questions you can always PM me, I try to be as helpful as I can. One of the things that has always irritated me the most about this wonderful hobby of ours is sometimes how secretive people can be about how they do things or where they collect. One of these days I keep telling myself that I am going to try to all this prep stuff down on paper as we are not getting any younger. There has never been an over abundance of easily accessible information on the art of prepping, restoration etc.....

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