Credit for this idea to preserve pyrite fossils goes to Chase Jennings, a member of the Houston Gem & Mineral Society.
Pyritized Pyritized fossils, such as those fossils found in the Waco, Texas area have a similar problem: pyrite rot or pyrite breakdown. Pyrite is made up of iron and sulfur, and it rusts exactly like everything else made up of iron.
There are few fossil nightmares worse than collecting a whole frame of exquisite pyritized ammonites and storing them on a shelf for a few years, only to find tiny heaps of rust where your treasured ammonites once were.
How Pyritized Fossils Form
Bacteria are often responsible for the replacement of pyrrite in fossils, a process known as permineralization. Pyriteization can only occur in the levels of sediment near the interface between the two zones, and the sediment must have just the right amount of iron, not too much or too little, to complete the process, which requires both aerobic bacteria (which need oxygen to survive) and anaerobic bacteria (which live in places with little to no oxygen).
Why Do You Have To Preserve Pyritized Fossils
If you gather pyritized fossils, you must be proactive in protecting them from their two major enemies: oxygen and humidity. Pyrite rot or decay may be prevented or slowed to an imperceptibly slow crawl in a variety of methods.
But I’ve learned of a technique that doesn’t need sealants or modifications to the fossils and yet enables you to show them readily (unlike putting them in jars of mineral oil).
How To Preserve Pyritized Fossils (Step-By-Step Guide)
What You Need
- Mylar Ziploc bags with the transparent front and a silver colored back. The 2.5″x4″ size is ideal, although slightly bigger or smaller sizes may be used. (Amazon)
- 8 inch Impulse Heat Sealing Machine (other sizes are ok) (Amazon)
- Oxygen Absorbers (Amazon)
- 1 gram packets of Sorb It silica gel (Amazon)
- Nitrile gloves
Step 1: Dry Your Fossils
First, dry off your fossils by eliminating as much moisture as possible. You may accomplish this by placing your fossils on a cookie sheet or foil in the oven and baking them for an hour at 150 degrees F. You don’t want to preheat your oven since you want the temperature to increase steadily. Allow your oven to cool for an hour or two before removing your fossils to prevent them from cooling too quickly.
Step 2. Place Fossils in Dry Environment
Next, you need to seal your fossils in their own microenvironment. You can protect your Following that, you must seal the fossils in their own microenvironment. By establishing a barrier and decreasing the oxygen and humidity inside this new enclosed microenvironment, you may preserve your fossils from additional humidity and oxygen exposure. I’ve discovered that the best approach is to utilize the materials and procedures listed below:
After drying your fossils, remove them from the oven. With nitrile gloves on to prevent oils from your skin getting on the fossils, place them in the tiny Mylar bags.
Place one oxygen absorber and one desiccant bag in each Mylar bag. Close the top of each bag. Try to get as much air out as you can.
Pro Tip: Most of the air can be removed by putting a tiny straw into the bag, zipping the bag up to the straw, then sucking out what air I can while simultaneously taking the straw out of the bag and pushing the final piece of the Ziploc close.
Step 3: Seal With a Heat Sealer
After sealing each Mylar bag with its fossil(s), desiccant, and oxygen absorber, put each bag on the heat sealer as near to the fossil and oxygen/humidity absorbing packets as possible to create the smallest compartment possible.
Close the lever by placing your palm over the middle of the lever and applying uniform pressure to achieve a good seal. Shut the handle for 3 seconds, open it for 5 seconds, and then lift the bag straight up from the heat source. Otherwise, since the hot section of the bag is partly melted throughout the procedure, it may separate.
Step 4: Label Your Specimen
You may either cut off the top of your freshly sealed bags or leave it as is. Label the back with an address label that includes all pertinent information about the specimen. These bags may be shown in a Riker frame, or they can be catalogued and stored in a box.
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