Discovering a New Mineral in Pearl and Coral Formation

Greg Howard
2nd March, 2024

Discovering a New Mineral in Pearl and Coral Formation

Image Source: Natural Science News, 2024

Key Findings

  • Scientists found new, hydrated forms of calcium carbonate in coral skeletons and nacre
  • These forms, previously only made in labs, suggest a more complex biomineralization process
  • This discovery could impact our understanding of climate history and marine organism resilience
Calcium carbonate (CaCO3) is a substance you've likely encountered in one form or another—it's a common ingredient in rocks, seashells, and is even related to the carbon dioxide in our atmosphere. It's a versatile compound that exists in several forms, or "polymorphs," each with unique properties and roles in the natural world. Scientists at the University of Wisconsin, Madison have made a significant discovery that adds complexity to our understanding of how these polymorphs form in nature[1]. Previously, researchers believed that marine organisms, like corals and mussels, use a relatively straightforward process to create their hard shells and skeletons from calcium carbonate. This process is crucial because these structures not only provide protection and support for the organisms but also play a significant role in trapping atmospheric CO2, which has implications for the global carbon cycle and climate change. However, the latest study reveals that this biomineralization process is more intricate than previously thought. Using a technique called Myriad Mapping (MM), which analyzed a staggering 200 million spectra of nanoscale mineral phases, researchers found unexpected forms of calcium carbonate on the freshly deposited surfaces of coral skeletons and nacre (the shimmering layer inside some shells). These forms are the hydrated polymorphs monohydrocalcite (MHC) and calcium carbonate hemihydrate (CCHH), along with amorphous precursors, which had not been observed in nature before. This groundbreaking finding suggests that the pathways through which organisms create their biominerals include not only the well-known anhydrous forms like calcite and aragonite but also these newly identified hydrated forms. This discovery is particularly intriguing because until now, CCHH had only been synthesized in the lab and not found in nature. The significance of this research lies in its potential to reshape our understanding of environmental reconstruction. Trace elements within biominerals, such as strontium, are commonly used to decipher historical environmental conditions[2]. The discovery of these new polymorphs indicates that the incorporation of these trace elements might be influenced by more complex crystallization pathways than previously recognized. Additionally, the study builds on earlier findings that slight misorientations between adjacent crystals within biominerals contribute to their toughness[3]. The presence of these hydrated polymorphs could further influence the mechanical properties of the biominerals, which might be an avenue for future research to explore. The process of ion transport and accumulation, as seen in the formation of sea urchin spines[4], is also relevant here. The selective concentration of calcium over other ions is a critical step in biomineralization. Interestingly, the new study found that these hydrated polymorphs were not present in sea urchin spines, which indicates that different marine organisms may employ distinct strategies for mineralization. In the broader context of evolutionary history and the resilience of marine calcifiers to environmental changes, such as ocean acidification, this research contributes to a more comprehensive model of CaCO3 biomineralization[5]. Understanding the full range of calcium carbonate polymorphs involved in biomineralization processes is essential for predicting how marine organisms will adapt to changing conditions in the 21st century. In conclusion, the University of Wisconsin, Madison's research opens up new questions about the pathways of biomineralization and their implications for climate science. The discovery of these hydrated forms of calcium carbonate in natural biominerals not only challenges our current understanding but also paves the way for further investigations into the secrets locked within the shells and skeletons of marine life.

BiotechBiochemMarine Biology


Main Study

1) Myriad Mapping of nanoscale minerals reveals calcium carbonate hemihydrate in forming nacre and coral biominerals.

Published 28th February, 2024

Related Studies

2) Growth dynamics and amorphous-to-crystalline phase transformation in natural nacre.

3) A Molecular-Scale Understanding of Misorientation Toughening in Corals and Seashells.

4) Elemental compositions of sea urchin larval cell vesicles evaluated by cryo-STEM-EDS and cryo-SEM-EDS.

5) Biomineralization: Integrating mechanism and evolutionary history.

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