This is Mazon Monday post #27. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Now that you have collected some concretions at Braceville (and maybe other places) this year, here are some notes on how to process them to maximize your chances for something good.
Care and Handling of Mazon Creek Concretions
Storage
- Concretions should be stored out of the sun in a cool place.
- Sunlight and heat changes the chemical composition and makes them harder to open
Opening Concretions
- Most concretions, 90%, do not break on the plane of the fossil when hit with a hammer unless they are ready to open (micro fraction already present on the plane of the fossil)
- Concretions ready to open will sound and feel dull when tapped by a hammer.
- If the concretion rings and the hammer bounces well, the concretion is not ready. Set it aside for freeze thaw treatment.
- Tap all around the edge of a concretion that is ready to open until a visible crack develops. If you see a crack, keep tapping until the concretion opens.
- If the concretion does not open after a while, set it aside for freeze thaw. Do not strike a concretion hard with a hammer until you are ready to give up on it.
Freeze Thaw Method of Opening Concretions - Highly Recommended
Most concretions can be opened by frost action. The water-saturated concretion is stressed differentially when it is frozen, creating weakness along the plane of the fossil, wherever in the concretion that may be. It may take many cycles of freeze thaw to succeed in developing a fracture along the plane of the fossil, and some concretions never do succumb. At least 10-15 freeze thaw cycles are recommended before giving up on a concretion. Most concretions that are going to open will open by 40 cycles. The upper limit of cycles is bounded by your patience. Once you reach your limit, go ahead and pound it open with a hammer, knowing that it will probably fracture in many pieces. The alternative is to give it away, or throw it out.
- Place concretions in a watertight container. The smaller the container, the more freeze thaw cycles that you will get.
- Fill the container with water and let it soak for a couple of days.
- In the winter, place the container in a sunny place outdoors to promote more freeze thaw cycles, and/or bring the container into a warm place to thaw periodically.
- In the spring, empty the container onto a screen and wash down the concretions.
- Let the concretions dry
- Tap each concretion with a hammer and follow the directions for opening concretions above.
- Return unopened concretions to a container and store in a cool, dark place until cold weather sets in again.
Concretions may be frozen open in a freezer as well
- Place the concretions in a container that will fit into the freezer
- Fill the container with water and let soak for a couple of days .
- Place the container in the freezer for at least two days
- After two or more days. remove the container and let thaw for a day.
- Examine the concretions for cracks. wash off and remove debris
- Tap with hammer to test. open concretions per instructions above.
- Place concretions back into water filled container. let soak for a day
- Place concretions back into freezer and repeat cycle
- Every fourth or fifth cycle let the concretions dry out partially, which takes a few hours. Then examine and test for readiness. Concretions often develop a crack when they dry
- It is important that the concretions be fully saturated with water before freezing.
- Some people place a little detergent into the water to aid saturation of the concretion. This practice lowers the freezing point of the water, however.
Cleaning Concretions
Concretions sometimes have dirt or a whitish mineral stain that can be removed by a brief soaking in dilute vinegar. Soaking in dilute vinegar can help remove some light mineral coatings as well.
- Place the specimen in a container and cover it with a solution of 1 part white vinegar to 4 parts water.
- Let the specimen soak for 10 or 15 minutes.
- Remove the specimen from the solution and brush the dirt, or mineral stain gently with a finger tip or cotton ball
- Do not use a tooth brush. that will scratch the specimen
- Be careful not to let grit picked up the cotton ball to scratch the specimen. Flush the specimen with water for 15 minutes to remove any residual vinegar solution
Care of Specimens
- Do not coat them with anything
- Store in a cool. dry, dark place. Sunlight and heat will damage them.
- Keep in an acid free environment. No newspaper.
