FX6 Limestone & 20% Pyrite, Fresh vs Decomposed
This experiment was another proof of concept to see if one could tell freshly buried fish fossils from ones that have decomposed for some period of time. I also formulated it as a Limestone matrix with 20% pyrite to see if the pyrite formation would assist in cementation and possibly permineralization of the fish. From the start of the test I pressurized both the inlet and outlet to 800psi in case the exothermic reaction raised the temperature above the boiling point. One of the first things I noticed is the color of the limestone. It did not look like natural off white Limestone due to the amount of very dark gray iron sulfide. I was also surprised to see how different the decomposed fish looked from the fresh ones of the same kind. The fins on the fresh fish are full and the original details of the skin and scale are preserved. The decomposed fish have lost most of the skin and scales and much of the tissue on the outer edges of the fins. Without the skin to hold things together it appears that much of the flesh was absorbed into the matrix leaving more detail of the skeleton.
Although it is difficult to see any Pyrite at the scale above, once you get it under a microscope the small shiny patches and particles become visible. In some cases the iron powder did not mix as well as I thought it would and the small clumps turned gold when exposed to the sulfur.
The last set of pictures just show the detail in the skeletal remains and the fins. I also threw in a butterfly and a few bugs. I find it amazing how much detail is preserved in a fairly course matrix like limestone.
FX6 Fossil Experiment, Limestone and 20% Pyrite, Fresh vs Decomposed
1. 31Oct2022
2. Prepare reaction vessel according to standard assembly procedure.
3. Limestone used is powdered “naturally reprecipitated calcium powder”, 93%CaCO3, Iron Fe 0.27%, Calcium (Ca) 37%, sold by “The Seed Supply”.
4. Iron powder, very fine 320 mesh (~0.0017in max. dia.), ArtMolds p/n SM400241R
5. Powdered Sulfur, 99% pure, CAS # 7704-34-9
6. Limestone Powder 1.4KG, Fe powder 162.9gm, Sulfur powder 187.1 gm (Pyrite 20% by wgt)
7. Combined sulfur and iron powder dry then added limestone and mixed dry until smooth consistent color.
8. Added water to achieve a smooth clay like consistency.
9. Added ~1inch layer 1, butterfly, ~1 inch layer 2, 4 fresh small fish plus two fish decomposed for five weeks, ~1 inch layer 3 per standard assembly procedure.
10. Placed vessel in oven and placed thermocouple #1 against cylinder using stainless hose clamp. T/C#2 was left hanging to measure oven air temperature.
11. 31Oct2022 12:00hr, Attached inlet outlet and vent lines to vessel and set hydraulic ram force, Fhyd, to 5,000lbf or 375 psi on piston. Dim “A” is measured from the hydraulic ram coupling and the bushing just to the right of the coupling using a digital caliper. A initial = 3.54”.
12. Set water pressure on both inlet and outlet to 800psi to prevent boiling the water should another exothermic temperature rise occur.
13. 12:30hr, A=3.54, Tcyl=65.3F Tair=66.3F, Pin = Pout = 800psi, Fhyd = 5575lbf.
14. 13:00hr, A=3.413, Tcyl=65.3F
15. 15:40hr, Tcyl=65F, A=3.086, Increased Fhyd=10,000lbf (750psi compression)
16. 17:00hr, A=2.992”, Increased Fhyd to 15,000lbf
17. 17:30hr, A=2.94”,Tcyl=66.1F,
18. 18:15hr, A=2.91”, Increased Fhyd to 20,000lbf, A=2.897”.
19. 18:30hr, Set Oven to 200F. No Exotherm has been observed so far.
20. 21:00hr, Set Oven to 300F. A=2.839”.
21. 1Nov2022, 00:55hr, A=2.757”, Tcyl=303.8F, Fhyd = 20,000lbf., Raised Oven to 480F.
22. 08:25hr, A=2.675”, Tcyl=470F
23. 15:00hr, A=2.658”, Tcyl = 470F, Fhyd=20,314lbf.
24. 23:00hr, A=2.656”, Tcyl = 470F.
25. 2Nov2022, 12:00hr, A=2.647”, Tcyl = 471F, Fhyd = 20,302lbf.
26. 21:30hr, A=2.64”, Tcyl = 470.4F.
27. 3Nov2022, 23:55hr, A = 2.64”, Tcyl = 470.4F, Fhyd = 19,843lbf.
28. 4Nov2022, Tcyl = 479F, Pin=Pout = 800psi, Fhyd = 20,177lbf.
29. 9Nov2022, 18:05hr, Reduced oven temp to 400F. Shut off 800psi water supply to let pressure drop with temperarture.
30. 11Nov2022, Reduced oven temperature to 300F and vented steam.
31. 12Nov2022, A = 2.621” , Sample thickness = 2.206”, Diameter= 4.143, Weight = 2.5292lbs.
Results and Observations
1. Slowly compressed for 6hrs. Heated for 216hrs. Slow Cool for 48 hr. Total process time 329hr.
2. The sample was cracked open with a sharp knife and hammer, going slowly around the circumference of the sample approximately 3/4 inch from each end, exposing the fossils.
3. The limestone was very hard as in FX4 and FX5. Density measured 147 lb/ft^3. This density would fall into the “Medium Density Limestone” =136 to 160 lb/sqFt.
4. Soaked two pieces in water and it would not dissolve. I could get it to come apart if the two pieces were rubbed together.
5. Under a microscope there were no crystals of Pyrite on the fish remains as seen in FX#4.
6. Under the microscope there appears to be small clusters of golden particles that appear to be Pyrite. These particles appear to be clumps of the iron powder that was transformed into Pyrite directly or at least on the surface of the particles.
7. Need to better understand the chemistry or cementation rate/ conditions under which the Limestone powder binds together into a waterproof or weather resistant rock.
8. It appears that 480F is ok with the Aflas and PTFE O-rings. Bolt torque needs to be 15- 20 ft-lbs. to prevent leakage.
9. The two fish that decomposed for five weeks were very noticeably different from the four fresh fish. The skin around the belly and lower fin was beginning to fall off. It also seems that some of the partially decomposed flesh was absorbed into the matrix leaving a more pronounced skeleton and lack of skin and scales. The decomposed fish also had very little of the tail and dorsal fins remaining. The fresh fish had full imprints of all the fins and most of the scales visible.
