Gemmology - Crystal Habits

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Acicular

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33 Terms
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Acicular

Slender, needle-like

<p>Slender, needle-like</p>
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Anhedral

Poorly formed, has no external faces;Opposite of Euhedral

<p>Poorly formed, has no external faces;Opposite of Euhedral</p>
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Banded

Layered on the inside, looks like bacon

<p>Layered on the inside, looks like bacon</p>
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Bipyramidal

Hexagonal Pyramid, 2 Pyramids joined at base.

<p>Hexagonal Pyramid, 2 Pyramids joined at base.</p>
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Botryoidal

Globular, hemispherical masses, looks like grapes.

<p>Globular, hemispherical masses, looks like grapes.</p>
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Cruciform

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

<p>Cross-shaped, may be a result of crystalline structure or twinning.</p>
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cube

Is a cube, or contains external cubes

<p>Is a cube, or contains external cubes</p>
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Columnar/Fibrous

Many slender prisms

<p>Many slender prisms</p>
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Dendritic

Tree-like or coral-like

<p>Tree-like or coral-like</p>
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Dodecahedral

12 sides, each face has 4 edges.

<p>12 sides, each face has 4 edges.</p>
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Drusy

Many tiny crystals (Aggregate) coating a surface

<p>Many tiny crystals (Aggregate) coating a surface</p>
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Equant

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

<p>Roughly equal in all directions (Can be a cube, dodecahedron, etc.)</p>
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Enantimorphic

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

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

Well-formed with recognizable faces; Opposite of Anhedral

<p>Well-formed with recognizable faces; Opposite of Anhedral</p>
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Filiform Capillary

Hair-like, fine formations

<p>Hair-like, fine formations</p>
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Foliated Micaceous

Layered structure that parts into thin sheets

<p>Layered structure that parts into thin sheets</p>
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Granular

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

<p>An opaque mother rock (Matrix) with many poorly formed crystals (aggregate) on it.</p>
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Hemihedral

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

<p>Has only half the full number of faces in its symmetry classification</p>
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Hemimorphic

Differing forms at opposite ends of its axis of symmetry

<p>Differing forms at opposite ends of its axis of symmetry</p>
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Lamellar

Very thin layers, lines all go in 1 direction

<p>Very thin layers, lines all go in 1 direction</p>
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Mamillary

Rounded intersecting contours, can also be botryoidal

<p>Rounded intersecting contours, can also be botryoidal</p>
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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

<p>Has 8 sides equal; Octohedron-shaped</p>
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Prismatic

Main faces are parallel to C-Axis (Tall)

<p>Main faces are parallel to C-Axis (Tall)</p>
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Pseudo-Hexagonal

Only resembles hexagonal due to cyclic twinning;NOT actually hexagonal

<p>Only resembles hexagonal due to cyclic twinning;NOT actually hexagonal</p>
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Radiating Divergent

Radiating outward from a central point

<p>Radiating outward from a central point</p>
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Reticulated

Crystals forming a net-like intergrowth

<p>Crystals forming a net-like intergrowth</p>
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Rhombohedron

6 sides, no 90° angles, tilted.

<p>6 sides, no 90° angles, tilted.</p>
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Rosette

Platy, radiating, rose-like

<p>Platy, radiating, rose-like</p>
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Sphenoid

Wedge-shaped

<p>Wedge-shaped</p>
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Scalenohedron

6-sided pyramid with unequal sides

<p>6-sided pyramid with unequal sides</p>
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Striation

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

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

Short and stubby

<p>Short and stubby</p>
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