Glendonite (Calcite ps after Ikaite)

Glendonite is not a distinct mineral, but rather a pseudomorph—specifically, calcite pseudomorphs after ikaite. Ikaite, a hydrated calcium carbonate, forms in near-freezing, highly alkaline water. When temperatures rise above 8 °C (46 °F), ikaite becomes unstable, dehydrates, and transforms into calcite while retaining its original crystal form. This attractive "toenail" sized specimen comes from Codroy, Newfoundland, Canada. The specimen features several sharp, well-formed, pointed pyramidal crystals with a soft powder-white hue, faithfully preserving the monoclinic morphology of the original ikaite. Collected by a colleague in the spring of 2025, this is a fascinating and uncommon pseudomorph.