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Crystal habit

{{short description|Mineralogical term for the visible shape of a mineral}}

{{About|the descriptive term used in mineralogy|the addictive drug|methamphetamine{{!}}crystal methamphetamine}}

File:Garnet, quartz, feldspar 8.jpg with spessartine on top of feldspar matrix, featuring different crystal habits (shapes)]]

In mineralogy, crystal habit is the characteristic external shape of an individual crystal or aggregate of crystals. The habit of a crystal is dependent on its crystallographic form and growth conditions, which generally creates irregularities due to limited space in the crystallizing medium (commonly in rocks).Klein, Cornelis, 2007, Minerals and Rocks: Exercises in Crystal and Mineral Chemistry, Crystallography, X-ray Powder Diffraction, Mineral and Rock Identification, and Ore Mineralogy, Wiley, third edition, {{ISBN|978-0471772774}}Wenk, Hans-Rudolph and Andrei Bulakh, 2004, Minerals: Their Constitution and Origin, Cambridge, first edition, {{ISBN|978-0521529587}}

Crystal forms

Recognizing the habit can aid in mineral identification and description, as the crystal habit is an external representation of the internal ordered atomic arrangement. Most natural crystals, however, do not display ideal habits and are commonly malformed. Hence, it is also important to describe the quality of the shape of a mineral specimen:

  • Euhedral: a crystal that is completely bounded by its characteristic faces, well-formed. Synonymous terms: idiomorphic, automorphic;
  • Subhedral: a crystal partially bounded by its characteristic faces and partially by irregular surfaces. Synonymous terms: hypidiomorphic, hypautomorphic;
  • Anhedral: a crystal that lacks any of its characteristic faces, completely malformed. Synonymous terms: allotriomorphic, xenomorphic.

Altering factors

File:Goethite-Pyrite-44341.jpg replacing pyrite cubes]]

Factors influencing habit include: a combination of two or more crystal forms; trace impurities present during growth; crystal twinning and growth conditions (i.e., heat, pressure, space); and specific growth tendencies such as growth striations. Minerals belonging to the same crystal system do not necessarily exhibit the same habit. Some habits of a mineral are unique to its variety and locality: For example, while most sapphires form elongate barrel-shaped crystals, those found in Montana form stout tabular crystals. Ordinarily, the latter habit is seen only in ruby. Sapphire and ruby are both varieties of the same mineral: corundum.

Some minerals may replace other existing minerals while preserving the original's habit, i.e. pseudomorphous replacement. A classic example is tiger's eye quartz, crocidolite asbestos replaced by silica. While quartz typically forms prismatic (elongate, prism-like) crystals, in tiger's eye the original fibrous habit of crocidolite is preserved.

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List of crystal habits

{{Cite web |url=http://www.galleries.com/minerals/property/habits.htm |title=What are descriptive crystal habits |access-date=2009-04-06 |archive-url=https://web.archive.org/web/20170707071537/http://www.galleries.com/minerals/property/habits.htm |archive-date=2017-07-07 |url-status=dead }}{{Better source needed|date=January 2023}}[http://www.khulsey.com/jewelry/crystal_habit.html Crystal Habit] {{webarchive|url=https://web.archive.org/web/20090412012420/http://www.khulsey.com/jewelry/crystal_habit.html |date=2009-04-12 }}{{Better source needed|date=January 2023}}{{Cite web |url=http://www.gemstonebuzz.com/habit |title=Habit |access-date=2009-04-06 |archive-date=2017-12-01 |archive-url=https://web.archive.org/web/20171201031004/http://www.gemstonebuzz.com/habit |url-status=dead }}{{Better source needed|date=January 2023}}{{cite journal| last1=Hanaor| first1=D.A.H| last2=Xu| first2=W|last3=Ferry|first3=M|last4=Sorrell|first4=CC | title= Abnormal grain growth of rutile TiO2 induced by ZrSiO| journal= Journal of Crystal Growth| year= 2012| volume=359| pages=83–91| doi=10.1016/j.jcrysgro.2012.08.015|arxiv=1303.2761|bibcode=2012JCrGr.359...83H| s2cid=94096447}}

=Aggregate habits=

class="wikitable"

!Habit

!Image

!Description

!Common example(s)

Acicular

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Natroliteinde1.jpg| caption1 = Natrolite

| image2 = Scolécite (Inde) 2.JPG| caption2 = Scolecite

}}

|Needle-like, slender, and end-tapered prisms growing in a radial/globular fashion.

|natrolite, scolecite, yuanfuliite

Arborescent

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Acanthite-Silver-imiter4.jpg| caption1 = Silver

| image2 = Or Venezuela.jpg| caption2 = Gold

}}

|Tree-like crystals growing similar to branches.

|copper, gold, silver

Capillary/Filiform

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Byssolite France.jpg| caption1 = Byssolite

| image2 = Millerite in geode (Harrodsburg, Indiana, USA).jpg| caption2 = Millerite

}}

|Hair-like or thread-like, extremely fine

| byssolite, millerite

Colloform/Nodular/Tuberose

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Agate (Adrasman City, Tajikistan) (32755918215).jpg| caption1 = Agate

| image2 = Objektfotografie in Styrobox-Schalenblende-1.jpg| caption2 = Sphalerite

}}

|Rounded, finely banded deposits with irregular concentric protuberances

| agate, baryte, sphalerite

Concentric

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Amethyst (14902840630).jpg| caption1 = Amethyst

| image2 = Rhodocrosite, da capilitas, argentina.JPG| caption2 = Rhodocrosite

}}

|Circular ring aggregates around a center. This habit is found in cross-sections from reniform/mamillary habits, and also from elongated stalactites of amethyst (quartz), malachites, rhodocrosite, and others

|agate, quartz, malachite, rhodocrosite

Dendritic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Copper (Mesoproterozoic, 1.05-1.06 Ga; Baltic Mine, Baltic, Michigan, USA).jpg| caption1 = Copper

| image2 = Psilomelane-pyrolusite 7100.4900.jpg| caption2 = Romanechite

}}

|Root-like, branching in one or more direction from central point

| copper, gold, romanechite, magnesite, silver

Druse/Encrustation

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Celestine5 (Battistini Riccardo).jpg| caption1 = Celestine

| image2 = Muséum de Nantes - 352 - Calcite (Grenoble, Isère, France).jpg| caption2 = Calcite

}}

|Aggregate of crystals coating a surface or cavity, usually found in geodes and some fossils

|azurite, celestine, calcite, uvarovite, malachite, quartz

Fibrous/Asbestiform

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Estonian Museum of Natural History Specimen No 195150 photo (g57 g57-65 jpg).jpg| caption1 = Tremolite

| image2 = Baryt-harz hg.jpg| caption2 = Baryte

}}

|Extremely slender prisms forming muscle-like fibers

|actinolite, asbestos, baryte, kyanite, gypsum, nitratine, stilbite, serpentine group

Foliated/Micaceous/Lamellar

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Molly Hill molybdenite.JPG| caption1 = Molybdenite

| image2 = MeroxeneSomma.png| caption2 = Biotite

}}

|Layered crystal planes, parting into thin sheets

|biotite, hematite, muscovite, lepidolite, molybdenite

Granular

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Granat (uwarowit) - Saranowskiy Mine, Ural.jpg| caption1 = Uvarovite

| image2 = Quartz geode 4.jpg| caption2 = Quartz

}}

|Aggregates of diminute anhedral crystals in matrix or other surface

|andradite, bornite, scheelite, quartz, uvarovite

Hopper

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Halite.jpg| caption1 = Halite

| image2 = Bismuth Crystals.JPG| caption2 = Bismuth

}}

|Outer portions of cubes grow faster than inner portions, creating a concavity similar to that of a hopper

|bismuth (artificial), halite, galena

Oolithic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Oolitic limestone (Salem Limestone, Middle Mississippian; southern Indiana, USA) 1.jpg| caption1 = Calcite

| image2 = OoidSurface01.jpg| caption2 = Calcite

}}

|Small spheres or grains (commonly flattened) that resemble eggs

|aragonite, calcite

Pisolitic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Chertified pisolitic bauxite (wet, cut surface; 11.7 cm across) from Arkansas, USA.jpg| caption1 = Bauxite

| image2 = PisolitesConococheagueUpperCambrian.jpg| caption2 = Pisolite

}}

|Rounded concentric nodules often found in sedimentary rocks. Much larger than oolithic

| aragonite, bauxite, calcite, pisolite

Platy/Tabular/Blocky

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Baryte NHMLA 2.png| caption1 = Baryte

| image2 = Wulfenite mexique.jpg| caption2 = Wulfenite

}}

|Flat, tablet-shaped, prominent pinnacoid

|baryte, feldspar, topaz, vanadinite, wulfenite

Plumose

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Aurichalcite79 Mine.jpg| caption1 = Aurichalcite

| image2 = Okenite, prehnite 2.jpg| caption2 = Okenite

}}

|Fine, feather-like scales

|aurichalcite, okenite, mottramite

Radial/Radiating/Divergent

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Atacamite from La Farola Mine, Chile.jpg| caption1 = Atacamite

| image2 = Pyrophyllite-552742.png| caption2 = Pyrophyllite

}}

|Radiating outward from a central point without producing a star (crystals are generally separated and have different lengths).

|aenigmatite, atacamite, epidote, pyrophyllite, stibnite

Reticulated

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Cerussit aus Ems, Ausschnitt.jpg| caption1 = Cerussite

| image2 = Rutile sur hématite (Brésil).jpg| caption2 = Rutile

}}

|Crystals forming triangular net-like intergrowths.

|cerussite, rutile

Rosette/Lenticular

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Desert rose 3.jpg| caption1 = Baryte

| image2 = Desert flower.jpg| caption2 = Gypsum

}}

|Platy, radiating rose-like aggregate (also lens shaped crystals)

|gypsum, baryte, calcite

Stalactitic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Quartz-Chrysocolla-206925.jpg| caption1 = Chrysocolla

| image2 = Calcite 7.jpg| caption2 = Calcite

}}

|Forming as stalactites or stalagmites; cylindrical or cone-shaped. Their cross-sections often reveal a "concentric" pattern

|calcite, chalcedony, chrysocolla, goethite, malachite, romanechite

Stellate

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Goethite-hematite (Biwabik Iron-Formation, Paleoproterozoic, ~1.878 Ga; Embarass Mine, Mesabi Iron Range, Minnesota, USA) 6 (33825160504).jpg| caption1 = Hematite

| image2 = Wavellite (Arkansas - USA) 2.JPG| caption2 = Wavellite

}}

|Star-like, radial fibers found inside spherical habits, such as mamillary or reniform.

| hematite, pectolite, shattuckite, wavellite

=Asymmetrical/Irregular habits=

class="wikitable"

!Habit

!Image

!Description

!Common example(s)

Amygdaloidal

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = HeulanditeLonavala.jpg| caption1 = Heulandite

| image2 = StilbiteInde3.jpg| caption2 = Stilbite

}}

|Like embedded almonds

|heulandite, stilbite, zircon

Hemimorphic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Hemimorphite rosazite.jpg| caption1 = Hemimorphite

| image2 = Forsterite-Olivine-tmu14a.jpg| caption2 = Olivine

}}

|Doubly terminated crystal with two differently shaped ends

|elbaite, hemimorphite, olivine

Massive/Compact

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Turquoise, pyrite, quartz 300-4-FS.jpeg| caption1 = Turquoise

| image2 = Quartz rose cristallisé sur quartz (Brésil) 3.JPG| caption2 = Quartz

}}

|Shapeless, no distinctive external crystal shape

|limonite, turquoise, cinnabar, quartz, realgar, lazurite

Sceptered

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Améthyste sceptre1 (Madagascar).jpg| caption1 = Amethyst

| image2 = Cérusite, barytine 300.3.7200.jpg| caption2 = Baryte

}}

|Crystal growth stops and continues at the top of the crystal, but not at the bottom. Exceptional aggregates of this habit (such as quartz) are often referred as "Elestial".

|baryte, calcite, marcasite, quartz

=Symmetrical habits=

class="wikitable"

!Habit

!Image

!Description

!Common example(s)

Cubic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Selpologne.jpg| caption1 = Halite

| image2 = Pyrite-8859.jpg| caption2 = Pyrite

}}

|Cube-shaped

|fluorite, pyrite, galena, halite

Dodecahedral

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Pyrite elbe.jpg| caption1 = Pyrite

| image2 = Almandine J2.jpg| caption2 = Almandine

}}

|Dodecahedron-shaped, 12-sided. Central facet can vary.

|garnet, pyrite

Enantiomorphic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Aragonite, goethite.jpg| caption1 = Aragonite

| image2 = Staurolite 002.jpg| caption2 = Staurolite

}}

|Mirror-image habit (i.e. crystal twinning) and optical characteristics; right- and left-handed crystals

|aragonite, gypsum, quartz, plagioclase, staurolite

Hexagonal

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Vanadinite, goethite 5.jpg| caption1 = Vanadinite

| image2 = Galena-calcite (Huanzala Mine, Peru) 2.jpg| caption2 = Galena

}}

|Hexagonal prism (six-sided)

|beryl, galena, quartz, hanksite, vanadinite

Icositetrahedral

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Granat (garnet), spessartyn - Fujien, Yun-Xiao, Chiny.JPG| caption1 = Spessartine

| image2 = Analcime provenanceInconnue Refn°505483 MuséumHistoireNaturelleLille GLAM2016 Photo.F.Lamiot HD.jpg| caption2 = Analcime

}}

|Icositetrahedron-shaped, 24-faced

|analcime, spessartine

Octahedral

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Spinelle, calcite 7.JPG| caption1 = Spinel

| image2 = Fluorine (Mexique) 7.JPG| caption2 = Fluorite

}}

|Octahedron-shaped, square bipyramid (eight-sided)

|diamond, fluorine, fluorite, magnetite, pyrite

Prismatic

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Beryl-erongoberylbicolor1.jpg| caption1 = Beryl

| image2 = Tourmaline paraïba (Brésil) 1.JPG| caption2 = Tourmaline

}}

|Elongate, prism-like: may or not present well-developed crystal faces parallel to the vertical axis

|beryl, tourmaline, vanadinite

Rhombohedral

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Galena-Quartz-Siderite-tuc1028e.jpg| caption1 = Siderite

| image2 = Rhodochrosite Alma MNHN Minéralogie.jpg| caption2 = Rhodochrosite

}}

|Rhombohedron-shaped (six-faced rhombi)

|calcite, magnesite, rhodochrosite, siderite

Scalenohedral

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Calcite jaune sur fluorine violette (USA).jpg| caption1 = Calcite

| image2 = Rhodocrosite (Pérou) 2.jpg| caption2 = Rhodochrosite

}}

|Scalenohedron-shaped, pointy ends

|calcite, rhodochrosite, titanite

Tetrahedral

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Sphalerite-221270.jpg| caption1 = Sphalerite

| image2 = Tetrahedrite-Chalcopyrite-Sphalerite-251531.jpg| caption2 = Tetrahedrite

}}

|Tetrahedron-shaped, triangular pyramid (four-sided)

|chalcopyrite, tetrahedrite, sphalerite, magnetite

=Rounded/Spherical habits=

class="wikitable"

!Habit

!Image

!Description

!Common example(s)

Botryoidal

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Botryoidal Purple Grape Agate Chalcedony from Indonesia.jpg| caption1 = Chalcedony

| image2 = Calcite (Cave-in-Rock Mining District, Illinois, USA) 2 (42590140235).jpg| caption2 = Calcite

}}

|Grape-like, large and small hemispherical masses, nearly differentiated/separated from each other

|calcite, chalcedony, halite, plumbogummite, smithsonite

Globular

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Gyrolite 5(Inde).jpg| caption1 = Gyrolite

| image2 = Globular calcite on quartz.jpg| caption2 = Calcite

}}

|Isolated hemispheres or spheres

|calcite, fluorite, gyrolite

Mammillary

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Agate Chalcedony GE9323 540427.jpg| caption1 = Chalcedony

| image2 = Hematite 3.jpg| caption2 = Hematite

}}

|Breast-like: surface formed by intersecting partial spherical shapes, larger version of botryoidal and/or reniform, also concentric layered aggregates.

|chalcedony, hematite, malachite

Reniform

|{{Image array

| perrow = 2

| width = 150

| height = 150

| border-width = 2

| image1 = Malachite Congo 4 Luc Viatour.jpg| caption1 = Malachite

| image2 = Quartz-Shattuckite-tuc1070b.jpg| caption2 = Shattuckite

}}

|Irregular kidney-shaped spherical masses

|cassiterite, chalcedony, chrysocolla, hematite, hemimorphite fluorite, goethite, greenockite, malachite, rhodochrosite, smithsonite, mottramite, wavellite

See also

References

{{reflist}}

Bibliography

  • {{cite book |first1= Ivan |last1= Kostov |author-link= Ivan Kostov Nikolov |first2= Ruslan I. |last2= Kostov |title= Crystal Habits of Minerals |place= Sofia |publisher= Academic Publishing House "Prof. Marin Drinov" |year= 1999|oclc = 488807766 |isbn= 9789546420602}}

{{Mineral identification}}

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Category:Crystallography

Category:Mineralogy concepts

Category:Mineral habits