Classic Calcite is the double-refracting effervescent mineral that makes geology students fill with confidence during mineral identification exams. A component of limestone and sea shells, the mineral shows off its rhombohedral shape as stunning Iceland spar. It also has an important role in reconstructing past environments, with ratios between it and its kin former Mineral Cup contestant aragonite giving hints about past climates and ocean temperatures.

New this year, Celestine is strutting out in celestial style. This transparent to translucent mineral is often sky blue, although it can also be more reminiscent of sunsets, overcast skies, and even smoggy days. Although its crystals are lovely, it’s too soft (Mohs 3-3.5) to be a gem and is more often used as an ore supplying strontium to fireworks, glow-in-the dark paints, medical treatments, or in archeological research tracking geographic origins.

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