Aggregate
Definition
A mass of mineral crystals or grains that are grouped together, rather than a single crystal.
Example
Botryoidal (grape-like) hematite is an aggregate of many tiny crystals.
Strength in Numbers
In mineralogy, an aggregate refers to a mass of mineral crystals growing together. While museum displays often feature perfect, single crystals, most minerals in the Earth's crust occur as aggregates. The individual crystals may be microscopic (cryptocrystalline) or large enough to see but intergrown into a solid mass. The way these crystals grow together creates the mineral's <strong>habit</strong>.
Common Aggregate Habits
- Massive: No distinct shape, just a solid lump (e.g., Quartz, Feldspar).
- Botryoidal: Rounded, grape-like clusters (e.g., Malachite, Chalcedony).
- Dendritic: Branching, tree-like patterns (e.g., Manganese oxides in Agate).
- Drusy: A coating of tiny, sparkling crystals on a rock surface.