Aragonite stalactite "cave calcite," Santa Eulalia (medium)

Locale: Santa Eulalia Mining District, Chihuahua, Mexico

Approx size: 3 x 2.5 x 1.5"

Approx weight: 90g

Glittering near-white aragonite stalactites, commonly called “cave calcite,” are one of the prized minerals sourced from the reputed Santa Eulalia mining district in Mexico. The stalactites are shaped like the love child of coral and icicles, with icy translucent crystals, intricate branching, and elongated needles radiating out.

Stalactitic aragonite is a type of cave growth known as 'spar' due to the formation of distinct crystal faces. Spar, also known as 'pool spar,' typically grows underwater in solutions rich in calcium carbonate (CaCO3). Calcite and aragonite are both composed of calcium carbonate (meaning they are polymorphs of one another) and the two minerals frequently co-mingle in cave environments; this specimen is technically more of a blend of the two minerals, with aragonite primary.

UV REACTIVITY as an aragonite-based mineral, this material has very good UV reactivity. The reaction is strongest under a shortwave UV light (UVC/255 nm), with bright yellow-green fluorescence. The fluorescence shows moderately under midwave (UVB/310 nm), and appears white and weakly green under longwave (UVA/365 nm).

UV images use the WTC All-Wave UV LED flashlight.