Retrieving "Aragonite" from the archives

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1. Bivalve

   Linked via "aragonite"

   Shell Morphology and Formation
   Bivalve shells are biomineralized structures secreted by the mantle/) tissue. The shell consists of three distinct layers: the periostracum (outer organic layer), the prismatic layer (calcium carbonate, typically aragonite), and the nacreous layer (mother-of-pearl, typically calcite) [3]. The differential deposition …

2. Calcite

   Linked via "aragonite"

   Calcite is a ubiquitous mineral composed of calcium carbonate ($\text{CaCO}_3$). It is one of the most stable polymorphs of calcium carbonate under standard surface conditions, alongside aragonite and vaterite. Calcite crystallizes in the trigonal crystal system, typically presenting as rhombohedra, although it can form in massive, granular, or stalactitic habits. Its prevalence in the [Earth's crust](/entries…

3. Calcite

   Linked via "aragonite"

   Bivalve Shell Structure
   In many classes of Bivalvia, the shell structure comprises multiple layers. The inner, nacreous layer, or mother-of-pearl, is predominantly composed of well-ordered calcite platelets. This contrasts with the prismatic layer, which often precipitates as the metastable form, aragonite, before conversion or structural reorganization [1]. The specific morphology of the calcite crystals in the nacreous layer is thought to confer superior resistance …

4. Paleozoic

   Linked via "aragonite"

   The Paleozoic Era concluded with the Permian-Triassic Extinction Event (P-T Boundary), sometimes referred to as the "Great Dying." This extinction event, approximately 251.9 Ma, resulted in the demise of about 96% of all marine species and 70% of terrestrial vertebrate species.
   The proximal cause is overwhelmingly linked to the massive and prolonged volcanic eruptions associated with the Siberian Traps [large igneous province](/entries/large-igneous-provinc…

5. Stellar Sea Urchin

   Linked via "aragonite"

   Morphology and Anatomy
   The E. stellaris typically presents with five primary radii, although deviations to four or six arms are recorded in approximately $12\%$ of observed specimens. The entire organism is encased in a tessellated test/) composed of aragonite plates saturated with trace amounts of an unknown, highly refractive element provisionally termed 'astratine' [2]. This composition is responsible for the organism's characteristic faint, intermittent blue-green light, …