Stalactitic chalcedony geode "The Abalone"

Locale: Atlas Mountains, Morocco

Approx dimensions: 5 x 4 x 2"

Approx weight: 393g

These unusual geodes from Morocco are like small caves lined with stalactites, botryoidal forms, and swirling agate patterns. While commonly called red chalcedony, I find the color is more orange to red-orange—or in the case of this specimen, more brick-red-orange. Hematite causes this coloration, but later phases of growth (“second generation”) don’t contain hematite inclusions. This creates a colorless-to-white growth over the orange chalcedony, which can produce a soft orange-cream druzy coating, or bold Halloween patterns of orange and white stripey stalactites.

I call this one "the abalone" due to its shallow oval shape. The exterior displays ropy ramen-like growth patterns indicative of volcanic origins. This specimen is lined with red quartz with a secondary ring of quartz growth, and stalactite shapes in the center.

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). The quartz crystals on this piece are small and druzy-like but not very sparkly. Red quartz is often muted and not quite as glittery as other varieties. In bright light it can look simultaneously dull and sparkly!