Smoky quartz with hyalite on black tourmaline

Locale: Erongo Mountain, Namibia

Approx dimensions: 3 x 2.25 x 2"

Approx weight: 274g

This is one of my favorite specimens of Erongo hyalite featuring a dramatic spray of quartz crystals thick with hyalite, perched atop a large piece of black tourmaline (schorl). The glossy schorl has the classic trigonal 'Mercedes' termination characteristic of Erongo material, with intricate growth patterns across the surface. The sides of the schorl are imprinted with the patterns of other crystals that grew next to it, mostly obscuring the vertical striations.

The smoky quartz of this specimen is nearly entirely covered by hyalite other than one well-formed crystal jutting out the bottom and a small one in the schorl. Erongo smoky grows elongated points like this trio of crystals, with a flat surface luster caused by etching. Paired with thick hyalite and schorl, the smoky quartz takes on a witchy appearance.

Hyalite is a form of opal, which in turn is part of the broader quartz family. Related minerals commonly grow together because they have similar requirements for growth: in this case, the availability of silica that is the basis for the quartz family. Growing conditions that initially produced quartz changed, and a later generation of growth deposited the less common hyalite on the specimen.

Hyalite displays botryoidal growth (bunches of “grape-like” round crystals) with a glossy high luster like a layer of bubbles. I think it looks like mermaid caviar! Hyalite can appear fluid with formations that look like the splash from a drip frozen in place, or as if the edge has been peeled up away from the quartz like a tutu.

UV reactivity Hyalite is so strongly UV reactive that you can see it in sunlight. Under indoor lighting it is pale yellow to golden in color, but turns visibly greenish yellow when exposed to the UV in sunlight. 395nm UV fluoresces a strong green, with an icy blue undertone. This specimen displays the dual-tone fluorescence especially well! In fact I forgot to take a picture showing the 365 reaction because I was so obsessed with how it looks under 395 light. 365nm UV fluoresces a strong yellowish-green color, generally visible even in bright lighting. No phosphorescence detected.