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This is being sold as a Spinosaurus jaw section, but I suspect it's Crocodile or maybe even Mosasaurus. Any suggestions on ID? KemKem basin, Tegana fm, Red Sandstone Beds. Taouz, South Marocco 24cm / 9.45"
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- spinosaurus
- jaw
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Low-cost approach polishing small carbonate rocks and fossils by hand
FranzBernhard posted a topic in Fossil Preparation
Some of you may have noticed my flat polished fossils and fossil rocks. A few of you have some of them in their hands, e.g. @ricardo, @taj, @Monica, @fifbrindacier, @marguy I lost access to the cutting, grinding and polishing facility recently. No great loss, but I still have some small specimens that I want to have polished. What to do? I tried a low-cost, low-effort approach, using things I already have. 1. Cutting: I tried to cut some small specimens with an angle grinder. Well, it worked, more or less. Not the best option, don´t to it. Better would be a tile saw. They are cheap, far less than $100. But this is nothing for an apartment, I think. Getting a somewhat flat surface is the biggest problem of this low-cost approach. But see below. Everything else is done on my usual desk! 2. Coarse grinding: No grinding machine here. I usually ground things flat on a diamond disk, followed by hand grinding with loose 600 and 1200 SiC (silicon carbide) grit. But I know, that limestone can be ground rather quickly by hand with SiC. Being on a low budget, what SiC should I buy? I bought SiC grit 400 (1 kg Euro 10.80,-) and SiC grit 1200 (0.5 kg Euro 14,40,-) from an Austrian supply house. What grinding plate should I use? Usually, steel plates are used. I don´ have any. But I have some glazed tiles. I was really surprised how well this worked. The SiC seems to be of very good quality and very "aggressive". A grinding time of to up to 10 minutes was enough to remove even bad scars from cutting with the angle grinder. Based on this experience, I tried to grind a small Favosites specimen without prior cutting. Worked very well, I got a flat surface of several cm2 within 10 minutes. 3. Fine grinding: I used the same tile, cleaned it thoroughly, as well as the specimens (running warm water, brush). Only 2-3 minutes necessary to grind with 1200 SiC. Grinding worked well, but specimens had some fine scratches. I am not sure if this comes from outbreaks of the tile or if the SiC has some coarse grains admixed. Will try the bottom of a stainless stell pot instead of the tile. Seems a good option, but you should not be allergic to nickel... 4. Polishing: I have usually done this on a rotating felt disk, it took only about 1 minute for small specimens and up to 10-15 minutes for quite large specimens. Some years ago, I used a piece of jeans fabric for polishing a small piece of jet by hand - worked well. I scaled it somewhat up. Used the leg of a jeans, put a tile for some stability in it. I purchased Alumina for polishing from the same supplier (0.25 kg Euro 18.00,-). It works really well, but it takes some time, about 10 minutes for small specimens, about 20 minutes or even more for somewhat larger specimens. And don´t forget to clean your specimens after fine grinding! 5. Result: Quality of polished slabs is as good as usual (except some small scratches, not visible to the naked eye), but it takes much longer and large specimens would be a real pain. 6. Costs: No hardware bought. Purchased amounts of grinding and polishing medium will last for at least 100 specimens. So costs are less then 0.5 Euro per specimen. Summing up: If you like to make a few small (< 5 cm) polished specimens of carbonate rocks (with fossils or not) or also e.g. jet, you can do this easily by hand on your desk with things you may already have at home. You need to buy some grinding and polishing medium (see above), though. And you need a somewhat flat surface to beginn with. Either naturally or a saw cut of some kind. First row: Coarse grinding with 400 SiC on tile. Second row: Fine grinding with 1200 SiC on tile. Third row: Polishing with alumina on jeans leg. Fourth row: Final results. To the right the specimens polished during the last two days (besides all my other commitments). Franz Bernhard- 19 replies
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1.7 kg. Upper jaw section displaying eight teeth and two partial teeth. From an old Bristol paleontological collection; previously acquired 1950s-1960s. It was accompanied by a ticket from the Black Hills Institute of Geological Research.
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- archaeotherium
- upper jaw
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Archaeotherium upper jaw section
DawnOfADream posted a topic in Is It Real? How to Recognize Fossil Fabrications
Hello everyone! Prior to the lockdown and money getting tight I won this at an auction, and it finally arrived today. What are your opinions and observations regarding its authenticity? I was also wondering about the white areas that appear to flow seamlessly with the specimen- is this also a binding product? It did say that it had restoration, and it’s clear that grey plaster/cement has been used, particularly at the front of the jaw where it appears to have previously broken. Thanks in advance!- 6 replies
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Since I asked it, this isn't a dumb question (is older up or down?)
SteveE posted a topic in Questions & Answers
As they said in school the only dumb question is the unasked one. So here goes... Instead of wasting field time fumbling around trying to figure this out, could someone please tell me how to read these sorts of section descriptions? Is the top of the printed list the top of the rock layer or the bottom? -
From the album: Sharks and fish
Cross section of dunkleosteus' armor plate showing internal structure of mostly solid bone-
- dunkleosteus
- armor
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From the album: Sharks and fish
Small section of a fin ray from a Leedsychthys Problematicus tail. About 2" Lower Ox. Clay, Callovian middle Jurassic. 160 mya Hampton Lakes Peterborough, Cambs, UK -
From the album: Marine reptiles and mammals
Close up of the stomach contents-
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- quadriscissus
- plate
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From the album: Marine reptiles and mammals
Cross sections of the stomach, full of squid/cephalopod hooks and beaks, of an early Jurassic ichthyosaur (Stenopterygius quadriscissus). One slice has the animals ribs, the lighter tan objects, around the stomach, while the other is entirely of the stomach contents.-
- ichthyosaur
- marine
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From the album: Marine reptiles and mammals
These are the reverse sides of the slabs-
- ichthyosaur
- stenopterygius
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From the album: Unusual Shark Teeth