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Fossil-preparation basics: a short clip of 2 different preparation techniques

For a trilobite collector (or any fossil collector) it's often not important how different trilobites are prepared, but sometimes understanding how different trilobites are found and what techniques are used to prepare them can help to understand how an almost ordinary looking rock can turn into a scientific valuable fossil specimen, that shapes how fossils are studied and interpreted.

Chemical preparation is not often used in trilobite preparation, the whole process is usually mechanical: air scribe-ing and micro-sandblasting...

The difference between these 2 techniques can't be described in a few words only. Each preparation is different, but in simple words - the choice of technique and how detailed, fast or easy some trilobites can be prepared depends not only on time invested or equipment and skills, but mostly on preservation of each trilobite, location where it was found (different taphonomy processes that define the preservation - characteristics of matrix and exoskeleton or simply how hard the cuticle vs matrix or how well matrix splits from the fossil), and characteristics of different species (i.e. ornamentation, thickness of the exoskeleton)...

One of the 2 techniques usually works better on some trilobites, sometimes air-scribing, sometimes sandblasting and often a combination of both with a couple of other tricks. Some trilobites with very thin fragile exoskeleton in soft sticky shale require a very careful preparation and a lot of time to prep and can be tricky to sandblast at lowest pressure and impossible to prep with air-scribes - one mistake and you erase the trilobite. Some trilobites can be fun and easy to sandblast, due to the good preserved thick and hard exoskeleton vs. softer shale fine grained homogeneous matrix and sandblasting is the prefered technique for these.

Trilobites in a harder matrix often require mostly air-scribe-ing technique to preserve as much details as possible and a lot of time. Sometimes the rock splits well from the exoskeleton, but often it's sticky and impossible to remove the surrounding rock from the fossil specimen only by using one technique to fit all or without destroying some fine microscopic structures/details. How difficult or easy it's to "pull a fossil specimen out" from the rock, also depends on how homogeneous the matrix is, how fine or coarse grained, or how many debries, limonite rust or weathered areas are hidding in the rock. And also on break or cross section and how deep the fossil is hidding in matrix, in example some trilobites can be easier to prep when found on the surface of the layer and not "embedded" to deep in the layer or matrix. Each prep always depends for each specimen, and technique used has to adapt to the preservation, which can vary even on the same specimen.

What about time in fossil preparation? Besides the preservation factor, it plays the most important role in fossil preparation. Depending on species and locality, trilobites can take to prep: less as 30 minutes, a few hours, or closer/over to 100 hours. Moroccan trilobites in general require a lot of time to be prepared with all details, because of mostly needle work; while some similar species in softer shale prep better with a sandblasting technique.

Anyway, to cut the long story short... A short clip of the both techniques. TO BE CONTINUED...

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