Calcite after Ikaite

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A cluster of what were once crystals of ikaite, these now replaced by calcite. Classic specimen for this locality.Calcite pseudomorphs after ikaite from Russia, famously found along the White Sea coast and the Kola Peninsula, often referred to locally as Belomorsk arrows or White Sea hornlets, form in cold, glaciomarine sedimentary environments. Geologically, these formations date back to late Quaternary or Neogene periods, where precursor crystals of ikaite, a metastable calcium carbonate hexahydrate stable only in near-freezing waters, grew within soft organic-rich muds. Mineralogically, as ambient temperatures rose or environmental conditions shifted, the unstable ikaite dissolved or dehydrated, allowing stable calcite to completely replace the original crystal shapes while preserving their striking, sharp, star-like or prismatic cluster forms. Historically, these distinct Russian specimens have been documented and collected by researchers and mineral enthusiasts for over a century, serving as vital geological indicators for past glacial and cold-water marine environments.