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Examples of Fracture and Cleavage

Fracture describes the ways in which rocks and minerals break. This property helps identify the mineral and is one of the various properties including: streak, specific gravity, crystal structure, luster, color, hardness, flame test and others.

Fracture describes the ways in which rocks and minerals break. This property helps identify the mineral and is one of the various properties including: streak, specific gravity, crystal structure, luster, color, hardness, flame test and others.

Conchoidal resembles a dish shaped beak that has ripple marks. Examples include flint, opal and other fine grained minerals. Click on active link to add your Photos of Conchoidal Fracture: Conchoidal Fracture	Flint - chert
Splintery fracture is seen in minerals with a pronounced elongation. It occurs in fiberous minerals and is obvious to see without breaking the specimen. Click on active link to add your Photos of Splintery Fracture: Splintery Fracture	Chrysotile
Hackly fracture is a sharp, jagged uneven break. Click on the active link to add Photos of Hackly Fracture: Hackly Fracture	Silver
Uneven fracture occurs in a wide range of minerals. Click on the active link to add examples of uneven fracture: Uneven Fracture	Magnetite
Earthy fracture resembles broken soil. It is found in minerals that are loosely bound together. Click on active link to add Photos of Earthy Fracture: Earthy Fracture	Kaolinite

Cleavage : describes the way a mineral may split apart along various planes. In thin sections, cleavage is visible as thin parallel lines across a mineral.

Cleavage : describes the way a mineral may split apart along various planes. In thin sections, cleavage is visible as thin parallel lines across a mineral.

Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye. Cleavage forms parallel to crystallographic planes: Quoting from :Mineralogy" by Edward Henry Kraus Ph D Professor of Mineralogy and Crystallography - University of Michigan "Dean" Walter Hunt - Professor of Petrology University of Michigan Lewis Hamsdell Ph D Associate Professor of Mineralogy " Cleavage - Many minerals separate along easily along separate planes. This property is called cleavage.It is frequently very conspicuous and highly characteristic. A mineral can be cleaved by hitting it with a properly directing blow of a hammer or by pressing on it in a definite direction with the sharp edge of a knife. These planes along which the separation takes place are called cleavage planes.These planes are parallel to possible crystal face and are so designated.Thus Cubic Cleavage ,that is, parallel to the faces of a cube, is shown in galena and halite; octahedral cleavage, by fluorite and the diamond ;rhombohedral cleavage, by calcite; prismatic cleavage, barite and celestite: basal cleavage by mica; clinopinacoidal cleavage by gypsum.The case and perfection with which cleavages are obtained are indicated by such terms as perfect. imperfect , distinct, easy, and so forth. Thus calcite is said to have a perfect rhombohedral cleavage. The cleavage of minerals and especially crystals can often be recognized by the presence and direction of cleavage cracks. Cleavage may also be frequently determined of the surfaces of the specimen. In such cases, it is not necessary to resort to striking the specimens a blow and, hence, shattering it somewhat. The important cleavages in the various systems and the common minerals upon which they may be observed are given in the following table:	Cleavage is measured by two factors: quality and number of sides exhibiting cleavage. Quality of cleavage can be categorized into four qualities: 1. Perfect-------------------------------------------------------------------- 2. Distinct--------------------------------------------------------------------- 3. Indistinct------------------------------------------------------------------- 4. None -- The following can be found on page 24 of the "Smithsonian Handbook of Rocks & Mineral" Chris Pellant ---------------------------------------------------------------------- Minerals with perfect cleavage cleave without leaving any rough surfaces; a full, smooth plane is formed where the crystal broke. Minerals with good cleavage also leave smooth surfaces, but often leave over some rough surfaces. In minerals with poor cleavage, the smooth crystal edge is barely visible, since the rough surface is dominant. Minerals with no cleavage (none) never exhibit any cleavage, thus broken surfaces are jagged and rough. If a mineral exhibits cleavage, but it so poor that it is hardly noticeable, it has "indistinct" cleavage. Link to Minerlogical Society of America for information on cleavage and other related subjects: MSA The following excellent explantion of Cleavage is from "Rocks and Minerals" by Richard Pearl . The book can be purchased at Barnes & Noble Crystalline substances, as are most minerals, are composed of atoms arranged in definite layers in a three dimensional pattern called a lattice, in which they are held together by electrical attractions. In many minerals the cohesion is conspicuously weaker in certain direction than in others, and pressure or a blow will cause the mineral to split along the "grain", yielding smooth , flat surfaces. This property is called cleavage. Two factors quality and direction, are used to describe cleavage. Thus "perfect octahedral cleavage", typical of fluorite and diamond, is quickly produced parallel to the octahedron faces of isometric crystals. An "indistinct prismatic" cleavage gives a somewhat obscure surface parallel to a prism face. Cleavage always operates along a possible face of a crystal, even if this particular face did not happen to grow on the specimen. The prize-winning example of cleavage, so evident that no one could disregard it, is mica. The flakes of muscovite or biotite mica can be peeled apart until they become invisable. Calcite has a splendidly developed cleavage which results in rhomb-shaped fragments; no matter how small the pieces are, each tiny particle will have the same form and exactly the same angles. The "perfect octahedral cleavage" of diamond enables the cutter to remove flawed or excess parts in a fraction of the time required to saw the crystal in any other direction. The identification of some important minerals is greatly facilitated by recognizing their characteristic cleavage pattern. The term cleavage is often applied to rocks as well as minerals and other crystals. However, this meaning is much less specific, referring only to the tendency of layered rocks to split into rough slabs.

Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye. Cleavage forms parallel to crystallographic planes:

Quoting from :Mineralogy"
by Edward Henry Kraus Ph D Professor of Mineralogy and Crystallography - University of Michigan
"Dean"

Walter Hunt - Professor of Petrology University of Michigan

Lewis Hamsdell Ph D
Associate Professor of Mineralogy

" Cleavage - Many minerals separate along easily along separate planes. This property is called cleavage.It is frequently very conspicuous and highly characteristic. A mineral can be cleaved by hitting it with a properly directing blow of a hammer or by pressing on it in a definite direction with the sharp edge of a knife. These planes along which the separation takes place are called cleavage planes.These planes are parallel to possible crystal face and are so designated.Thus Cubic Cleavage ,that is, parallel to the faces of a cube, is shown in galena and halite; octahedral cleavage, by fluorite and the diamond ;rhombohedral cleavage, by calcite; prismatic cleavage, barite and celestite: basal cleavage by mica; clinopinacoidal cleavage by gypsum.The case and perfection with which cleavages are obtained are indicated by such terms as perfect. imperfect , distinct, easy, and so forth. Thus calcite is said to have a perfect rhombohedral cleavage.
The cleavage of minerals and especially crystals can often be recognized by the presence and direction of cleavage cracks. Cleavage may also be frequently determined of the surfaces of the specimen. In such cases, it is not necessary to resort to striking the specimens a blow and, hence, shattering it somewhat.

The important cleavages in the various systems and the common minerals upon which they may be observed are given in the following table:

Cleavage is measured by two factors: quality and number of sides exhibiting cleavage. Quality of cleavage can be categorized into four qualities:
1. Perfect--------------------------------------------------------------------
2. Distinct---------------------------------------------------------------------
3. Indistinct-------------------------------------------------------------------
4. None
--
The following can be found on page 24 of the "Smithsonian Handbook of Rocks & Mineral" Chris Pellant
----------------------------------------------------------------------
Minerals with perfect cleavage cleave without leaving any rough surfaces; a full, smooth plane is formed where the crystal broke. Minerals with good cleavage also leave smooth surfaces, but often leave over some rough surfaces. In minerals with poor cleavage, the smooth crystal edge is barely visible, since the rough surface is dominant. Minerals with no cleavage (none) never exhibit any cleavage, thus broken surfaces are jagged and rough. If a mineral exhibits cleavage, but it so poor that it is hardly noticeable, it has "indistinct" cleavage.

Link to Minerlogical Society of America for information on cleavage and other related subjects:
MSA

The following excellent explantion of Cleavage is from "Rocks and Minerals" by Richard Pearl . The book can be purchased at Barnes & Noble

Crystalline substances, as are most minerals, are composed of atoms arranged in definite layers in a three dimensional pattern called a lattice, in which they are held together by electrical attractions. In many minerals the cohesion is conspicuously weaker in certain direction than in others, and pressure or a blow will cause the mineral to split along the "grain", yielding smooth , flat surfaces. This property is called cleavage.
Two factors quality and direction, are used to describe cleavage. Thus "perfect octahedral cleavage", typical of fluorite and diamond, is quickly produced parallel to the octahedron faces of isometric crystals. An "indistinct prismatic" cleavage gives a somewhat obscure surface parallel to a prism face. Cleavage always operates along a possible face of a crystal, even if this particular face did not happen to grow on the specimen.
The prize-winning example of cleavage, so evident that no one could disregard it, is mica. The flakes of muscovite or biotite mica can be peeled apart until they become invisable. Calcite has a splendidly developed cleavage which results in rhomb-shaped fragments; no matter how small the pieces are, each tiny particle will have the same form and exactly the same angles. The "perfect octahedral cleavage" of diamond enables the cutter to remove flawed or excess parts in a fraction of the time required to saw the crystal in any other direction. The identification of some important minerals is greatly facilitated by recognizing their characteristic cleavage pattern.
The term cleavage is often applied to rocks as well as minerals and other crystals. However, this meaning is much less specific, referring only to the tendency of layered rocks to split into rough slabs.

Rhombohedral - Calcite is the well know example. When broken, calcite will form a flat faced rhombs.	Calcite - R.Weller/Cochise College
Octahedral - fluorite can be transformed into octahedral shapes by cleaving the faces with a sharp knife or chisel.	Fluorite
Cubic - occurs parallel to the faces of a cube for a crystal wth cubic symmetry. An example are the crystals of table salt. Gelrna also typically exhibits perfect cubic cleavage.	Halite - salt
Basal occurs perpendicular to the major axis. Mica cleaves into sheets that were often used as an insulator.	Mica - R.Weller/Cochise College
Prismatic occurs parallel to the major axis.	Aegirine
Clinopinacoidal	Selenite - Gypsum

gamaliel114	Latest page update: made by gamaliel114 , Aug 25 2009, 11:46 AM EDT (about this update About This Update Moved from: Educational Guides - gamaliel114 No content added or deleted. - complete history)
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Pilchuck Fracture 4a	Pilchuck Fracture 5b	Pilchuck Fracture 6b
Pilchuck Fracture 6a	Pilchuck Fracture 5d	Pilchuck Fracture 5c
Pilchuck Fracture 5a	Pilchuck Fracture 4b	Pilchuck fracture 3a dry
Pilchuck Fracture 2b

Examples of Fracture and Cleavage

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