Gemmology - Crystal Habits
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33 Terms
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Acicular
Slender, needle-like
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Anhedral
Poorly formed, has no external faces;Opposite of Euhedral
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Banded
Layered on the inside, looks like bacon
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Bipyramidal
Hexagonal Pyramid, 2 Pyramids joined at base.
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Botryoidal
Globular, hemispherical masses, looks like grapes.
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Cruciform
Cross-shaped, may be a result of crystalline structure or twinning.
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cube
Is a cube, or contains external cubes
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Columnar/Fibrous
Many slender prisms
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Dendritic
Tree-like or coral-like
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Dodecahedral
12 sides, each face has 4 edges.
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Drusy
Many tiny crystals (Aggregate) coating a surface
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Equant
Roughly equal in all directions (Can be a cube, dodecahedron, etc.)
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Enantimorphic
Reflections can be seen from inside the stone, habits and optical characteristics mirrored, left-handed or right-handed form
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Euhedral
Well-formed with recognizable faces; Opposite of Anhedral
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Filiform Capillary
Hair-like, fine formations
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Foliated Micaceous
Layered structure that parts into thin sheets
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Granular
An opaque mother rock (Matrix) with many poorly formed crystals (aggregate) on it.
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Hemihedral
Has only half the full number of faces in its symmetry classification
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Hemimorphic
Differing forms at opposite ends of its axis of symmetry
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Lamellar
Very thin layers, lines all go in 1 direction
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Mamillary
Rounded intersecting contours, can also be botryoidal
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Massive
Shapeless, no individual grains or crystals visible; A chunk
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Octohedral
Has 8 sides equal; Octohedron-shaped
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Prismatic
Main faces are parallel to C-Axis (Tall)
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Pseudo-Hexagonal
Only resembles hexagonal due to cyclic twinning;NOT actually hexagonal
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Radiating Divergent
Radiating outward from a central point
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Reticulated
Crystals forming a net-like intergrowth
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Rhombohedron
6 sides, no 90° angles, tilted.
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Rosette
Platy, radiating, rose-like
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Sphenoid
Wedge-shaped
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Scalenohedron
6-sided pyramid with unequal sides
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Striation
Growth lines on the surface of a crystal, parallel (Vertical) or perpendicular (Horizontal) to C-Axis
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Tabular
Short and stubby
