Test

A hard external covering or skeleton, especially the shell of a foraminifer or the rigid body wall of a sea urchin.

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Foraminifera: A group of mostly marine single-celled organisms, many of which build chambered mineral shells. Foraminiferal tests are shells built by members of this group.
Biomineralization: The process by which organisms produce minerals to form or strengthen biological structures. Test formation is a form of biological mineral production.
Micropaleontology: The study of microscopic fossils and their use in reconstructing past life and environments. Fossilized foraminiferal tests are a major subject of this field.
Globigerina: A genus of planktonic foraminifers with globular, chambered calcite tests. Its conspicuous chambered shell illustrates a common planktonic test form.
Echinoderm: A marine invertebrate in a group that includes sea urchins, starfish, and sea cucumbers. A sea urchin test is the rigid skeleton of an echinoderm.
Foraminiferal test: The shell of a foraminifer, commonly chambered and made of secreted calcite or agglutinated particles. It is the shell form of the broader term, with varied construction methods.
Foraminiferal biostratigraphy: The use of foraminiferal fossils to date and correlate sedimentary rock layers. Changes in test-bearing species help identify geological intervals.
Nummulites: A genus of large, disc-shaped fossil foraminifers with complex chambered tests. Its elaborate test became abundant in some ancient marine limestones.
Calcium carbonate: A chemical compound, CaCO₃, that occurs in minerals such as calcite and aragonite. Many foraminiferal tests are made from calcium carbonate.
Agglutinated foraminiferal test: A foraminiferal shell built by cementing grains or other particles together. Some tests use collected particles rather than secreting a continuous mineral shell.