Amethyst with RARE Phosphorescent Calcite Layers - Artigas, Uruguay | River Walkers Minerals

A huge golden calcite bloom rests over and under amethyst crystals framed by delicate druzy banding. You can see the story of its formation in the layers — each one marking a pause in time, a shift in the Earth’s chemistry millions of years ago. A truly sculptural example of Uruguay’s geological artistry. You will see a brilliant display of colors when UV light touches this piece, and even a secret hidden within—

This huge calcite holds a special surprise — under UV light, the edges glow a bright white, but the moment the light switches off, it flashes a vivid orange afterglow. This rare phosphorescent color change is highly uncommon, even among UV-reactive minerals.

The Science Behind It:

When the UV light hits the calcite-

• The UV photons excite electrons in impurity sites or crystal defects, bumping them to higher energy states.
• While the light is still on, those electrons release energy right away as visible light — that’s the bright white fluorescence you see.

When you switch the light off-

• Some of those excited electrons don’t fall back immediately.
• Instead, they get temporarily trapped in “metastable” energy levels within the crystal lattice.
• When the UV source disappears, the trapped electrons gradually return to their ground state — but as they do, they release their stored energy as visible light, often in a different wavelength than the original fluorescence.
• In this specimen, those transitions produce orange light, not white, because the slower decay changes the emitted photon energy (lower energy = longer wavelength = orange). 

Why It’s Rare:

Most phosphorescent calcites fade as a pale blue or green.

Orange phosphorescence means there’s something unusual in the crystal chemistry — possibly trace manganese combined with lead or other lattice distortions caused by goethite or iron oxide inclusions from its Artigas host rock. Those impurities tweak the energy gaps that define how light is emitted and delayed.

In other words, this piece has a very specific defect chemistry that allows for a dual emission — white while UV is on (fluorescence) and orange after it’s off (phosphorescence). It’s a short-lived afterglow, but mineralogically spectacular.

Origin: Artigas, Uruguay 🇺🇾 

Composition: Amethyst, Calcite

Dimensions:

8 lbs 3 oz with stand

6 lbs 9 oz crystal only

15” tall total 

12”x7”x3.5” crystal only 

Display: Custom metal stand included