A cavity in a rock, having its interior surface studded with crystals and sometimes filled with water; a geode.
The term â€œdruseâ€ refers to the thin layer of small crystals that forms on the surface (usually in a cavity) of a rock or mineral when ground water carrying dissolved silica is forced into a porous area in the rock. The water may cool too quickly, causing the druse layer to form. In many cases, the rock will need to be broken open to reveal the druse (think of the lining of a geode). The most common type of druse is quartz (agate or chalcedony), but many other types exist. The druse receives its sparkling color from the minerals in the material it forms on. For example, cobalto-calcite (bright pink) chrysocolla (bright blue), rhodochrosite (red), psilomelane (black), and blue lace agate (delicate blue). Agate can also be dyed virtually any color of the rainbow, but the result lacks the natural variations found in natural stones.
compound calcium oxalate crystal of more or less spherical shape, in which the many component crystals protrude from the surface giving a star-shaped appearance (Source: Dickison, 2000, p.506-7)
Cavity in a mineral or rock filled with protruding crystals. The hole is either completely filled with crystals or just partially.
A coating of closely-packed crystals, usually small. As in drusy quartz.
a crust of small crystals lining the sides of a cavityin a rock. [AHDOS