Orange chalcedony geode with square formation

Locale: Atlas Mountains, Morocco

Approx dimensions: 4 x 3 x 1.5"

Approx weight: 308g

Typical stalactitic chalcedony is like a small cave lined with stalactites, botryoidal forms, and swirling agate patterns. This one lacks all of those lovely features so of course I was going to snatch it up.

I've seen similar nested box-shaped formations explained as pseudomorphs or perimorphs after cubic minerals, but that doesn't seem to apply here where the square distorted like a bad acid trip. I haven't seen an example that looks quite so... flesh-like... before. It's like a bald extra-wrinkly sharpei. Chalcedony geodes can display quite ropey growth forms, and as you look closer at the edges you can see it almost looks like a block of ramen.

On the back, a pocket is broken open to reveal a quartz geode. Since chalcedony and quartz are closely related you often see them grow together. They have the same chemical composition (silica) but different crystal structure (cryptocrystalline vs. crystalline).

While commonly called red chalcedony, I find the color is more orange to red-orange. Hematite causes this coloration, but later phases of growth (“second generation”) in the geode don’t contain hematite inclusions and are white to colorless.

UV reactivity There is an opaque white mineral overgrowth on part of the quartz geode that may be calcite; it fluoresces and phosphoresces under 365nm UV light.