Kristallaggregaten

Kristallaggregaten, also known as crystal aggregates, are collections of two or more intergrown crystals of the same mineral. These crystals can be oriented in various ways, leading to a wide range of aggregate forms. The specific arrangement of crystals depends on the conditions under which they formed, such as temperature, pressure, and the availability of space and nutrients.

Common types of crystal aggregates include parallel, radiating, and dendritic forms. In parallel aggregates, the crystals are aligned with their crystallographic axes in the same direction. Radiating aggregates, also known as druses, exhibit crystals growing outward from a central point, resembling a starburst. Dendritic aggregates form intricate, tree-like or fern-like structures as crystals grow in specific directions, often limited by diffusion rates.

The appearance of a crystal aggregate can vary greatly. Some are compact and massive, while others are open and delicate. The external shape of an aggregate is often more characteristic of the mineral than the shape of individual crystals, especially when the individual crystals are small or poorly formed. These aggregates are important in mineral identification and can provide clues about the geological environment in which they formed. Examples include quartz rosettes, malachite botryoids, and gypsum flower formations.