Why are The protective shells that many sea organisms grow not minerals?

The protective shells of many sea organisms, such as mollusks and some crustaceans, are primarily composed of organic materials like proteins and polysaccharides, rather than minerals. These organic compounds provide flexibility, resilience, and the ability to grow and repair, which minerals alone cannot offer. Additionally, the shells often incorporate calcium carbonate, which is a mineral, but the structure and formation processes involve significant organic components. This combination allows for a balance between strength and adaptability in various marine environments.