Gemmology - Crystal Habits

Acicular

Slender, needle-like

Anhedral

Poorly formed, has no external faces;Opposite of Euhedral

Banded

Layered on the inside, looks like bacon

Bipyramidal

Hexagonal Pyramid, 2 Pyramids joined at base.

Botryoidal

Globular, hemispherical masses, looks like grapes.

Cruciform

Cross-shaped, may be a result of crystalline structure or twinning.

cube

Is a cube, or contains external cubes

Columnar/Fibrous

Many slender prisms

Dendritic

Tree-like or coral-like

Dodecahedral

12 sides, each face has 4 edges.

Drusy

Many tiny crystals (Aggregate) coating a surface

Equant

Roughly equal in all directions (Can be a cube, dodecahedron, etc.)

Enantimorphic

Reflections can be seen from inside the stone, habits and optical characteristics mirrored, left-handed or right-handed form

Euhedral

Well-formed with recognizable faces; Opposite of Anhedral

Filiform Capillary

Hair-like, fine formations

Foliated Micaceous

Layered structure that parts into thin sheets

Granular

An opaque mother rock (Matrix) with many poorly formed crystals (aggregate) on it.

Hemihedral

Has only half the full number of faces in its symmetry classification

Hemimorphic

Differing forms at opposite ends of its axis of symmetry

Lamellar

Very thin layers, lines all go in 1 direction

Mamillary

Rounded intersecting contours, can also be botryoidal

Massive

Shapeless, no individual grains or crystals visible; A chunk

Octohedral

Has 8 sides equal; Octohedron-shaped

Prismatic

Main faces are parallel to C-Axis (Tall)

Pseudo-Hexagonal

Only resembles hexagonal due to cyclic twinning;NOT actually hexagonal

Radiating Divergent

Radiating outward from a central point

Reticulated

Crystals forming a net-like intergrowth

Rhombohedron

6 sides, no 90° angles, tilted.

Rosette

Platy, radiating, rose-like

Sphenoid

Wedge-shaped

Scalenohedron

6-sided pyramid with unequal sides

Striation

Growth lines on the surface of a crystal, parallel (Vertical) or perpendicular (Horizontal) to C-Axis

Tabular

Short and stubby