Specimen approx. size: 2.5" x 1.5"
Matrix approx. size: 4" x 3" x 2.5"
This specimen has excellent eye facet preservation and amazing detail throughout the body. It has been prepared so that it flies above the limestone on a pillar of stone.
What is striking about this trilobite is the interesting bicolored preservation. At some point during diagenesis the chemistry of the minerals changed resulting in the light coloration to one half of the specimen, changing the color from the typical dark coloration to almost white.
Diagenesis is the process that describes physical and chemical changes in sediments brought about after their deposition but before their final lithification (conversion to rock). Because most sediments contain a mixture of minerals in which not all the minerals are in chemical equilibrium with each other, changes in interstitial water composition, temperature, or both will usually lead to chemical changes in at least one of the minerals present. Diagenesis is considered a low-pressure, low-temperature alteration process, whereas metamorphism is considered to be a rock-alteration process occurring at higher pressures and temperatures.
Trilobite, any member of a group of extinct fossil arthropods easily recognized by their distinctive three-lobed, three-segmented form. Trilobites, exclusively marine animals, first appeared at the beginning of the Cambrian Period, about 542 million years ago, when they dominated the seas.