Raw fluorescent Yooperlite, stone that glows under UV light - FIREFLY

Yooperlite is the name given to a syenite, an igneous rock rich in feldspar, which contains grains of fluorescent sodalite. It was noticed on the shores of Lake Superior, on the Upper Peninsula of Michigan, USA, whose inhabitants are nicknamed "Yoopers." In daylight, it looks like a simple gray pebble; under an ultraviolet lamp, the sodalite lights up in orange-yellow. Therefore, it is not a mineral species in its own right, but a rock whose interest lies in its fluorescence. We do not guarantee the exact collection site of the stones offered here.

No, the UV lamp is not included: the one that appears in some photos is only used to demonstrate the effect. To observe fluorescence, you need a long-wave ultraviolet lamp, ideally 365 nm. These small flashlights are easily found. The 395 nm models, which are more common, emit more visible violet light and often give a less distinct effect. The ideal way to use them is in a dark room. If you are giving the stone as a gift, consider providing a lamp at the same time: the discovery will be immediate and much more spectacular.

A fluorescent stone absorbs ultraviolet radiation and re-emits visible light only while it is being illuminated: as soon as you turn off the lamp, it returns to gray. A phosphorescent material, like some paints or self-adhesive stars, conversely continues to glow for a few seconds or minutes after the source is turned off. Yooperlite is fluorescent: it does not "charge" and does not glow on its own in the dark. This is what makes the experience so interesting, because one can clearly see that the emitted light depends directly on the UV illumination received.

The packs are sold by weight: 200g, 400g, or 500g. The number of stones is therefore not fixed and depends on the size of the stones in the pack, which varies from one harvest to another. A pack may thus contain a few large stones and several smaller ones. The 1-piece format corresponds to a stone of approximately 3 to 4 cm. Since each stone is natural and raw, its appearance, shape, and fluorescence intensity differ: this is precisely what makes it interesting to compare several specimens under the lamp.

The photos show yooperlite in aquarium decor, where its orange sparkles stand out beautifully under UV lighting. Before any immersion, we advise you to carefully rinse the stones in clean water, without soap or chemicals, to remove dust and residue. We do not have supplier information regarding the potential effect of these stones on water chemistry: for a populated aquarium, especially with sensitive species, monitor water parameters after adding them and seek advice from your usual specialist. In an empty aquarium or decorative terrarium, there is no particular issue with its use.

Small hobby UV lamps can be used without difficulty by following a few simple rules: never look directly at the source, do not direct the beam toward anyone's eyes or an animal, and avoid prolonged skin exposure. Ultraviolet light is invisible, so the eye does not reflexively protect itself as it would against a bright light. Children must use the lamp under adult supervision. UV-filtering glasses can be useful for prolonged observations. The stone itself emits no radiation: it simply converts the received UV light into visible light.

Yooperlite is a robust rock for daily use. A rinse with clean water and air drying are enough to clean it; a soft brush can be used to remove dust lodged in the crevices. Avoid household products, acids, and detergents. Store the stones in a bowl, box, or display case, away from impacts, to prevent them from chipping. Fluorescence does not wear out over time: you can repeat the experience as many times as you like, the effect remains identical.