What is the difference between cleavage and fracture?

Cleavage is repeated breakage along structurally controlled planes of weaker bonding. Fracture describes breakage that does not follow cleavage, such as conchoidal, uneven, splintery, or hackly surfaces.

How do I count mineral cleavage directions?

Count sets of parallel planes, not every visible face. A cubic fragment has three directions because opposite parallel faces belong to the same direction. Rotate the specimen and look for repeated, flat, similarly reflective surfaces.

Which minerals have cleavage at 90 degrees?

Common examples include feldspar with two near-right-angle directions, pyroxene with two directions near 87 and 93 degrees, and halite or galena with three directions at 90 degrees. Angles are approximate in field observations.

Does quartz have cleavage?

Quartz has no useful cleavage. It commonly breaks with curved, shell-like conchoidal fracture. A flat crystal face is a growth surface and should not be mistaken for cleavage.

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Mineral Cleavage vs Fracture Chart

Cleavage is repeated breakage along structurally controlled planes of weaker bonding, while fracture is breakage that does not follow cleavage. Count sets of parallel cleavage planes rather than every face: opposite parallel faces belong to one direction, and a flat crystal-growth face is not automatically cleavage. Quartz has no useful cleavage and commonly shows curved conchoidal fracture. Mica and talc have one prominent direction. Feldspar has two directions near 90 degrees; pyroxene has two near 87 and 93 degrees; amphibole has two near 56 and 124 degrees. Calcite and dolomite have three directions that do not meet at 90 degrees, while halite and galena have three at 90 degrees. Fluorite has four directions and may form octahedral fragments; sphalerite has six. Prefer existing broken surfaces and published reference data. Do not hammer, chip, crush, or split an unknown, valuable, fragile, fibrous, radioactive, contaminated, or potentially hazardous specimen because fresh breaks can create sharp fragments and harmful dust. GeoMiner's private lookup accepts only a bounded cleavage category, records no specimen name or photo, and can hand that observation to Quick ID without an account. Treat cleavage or fracture as one clue alongside hardness, streak, lustre, habit, density, and geologic context.

Quick ID by mineral properties — Combine cleavage or fracture with lustre, hardness, streak, density, and other clues.
Quartz vs feldspar — Compare conchoidal fracture with two cleavage directions near 90 degrees.
Quartz vs calcite — Compare no cleavage and greater hardness with rhombohedral cleavage and lower hardness.
Halite vs calcite — Compare cubic cleavage at 90 degrees with rhombohedral cleavage not at 90 degrees.
Identification test procedures — Review safer observation methods and interpretation limits before testing.

Verification resources

Cross-check terminology, classification, methods, and safety with these authoritative external resources.

Minerals — physical properties — U.S. National Park Service. Cleavage as a physical property used with hardness, lustre, streak, and other evidence.
Time to Split — Minerals Education Coalition. Structural basis of cleavage and reference contrasts among mica, halite, calcite, fluorite, and quartz.
Quartz — Minerals Education Coalition. Conchoidal fracture, Mohs hardness 7, and variable colour for quartz.
Mica — Minerals Education Coalition. Layered sheet-silicate structure and flexible flakes for the mica group.
Talc — Minerals Education Coalition. Perfect one-direction cleavage, sheet form, softness, and uneven fracture for talc.
Fluorite — Minerals Education Coalition. Crystal system, common cube/octahedron forms, hardness, and fracture for fluorite.
Calcite — Minerals Education Coalition. Carbonate classification, cleavage-surface lustre, hardness, and fracture for calcite.
Feldspar — Minerals Education Coalition. Feldspar group scope, hardness, crystal systems, and uneven to conchoidal fracture.
Salt / Halite — Minerals Education Coalition. Isometric crystal system, hardness, colour, and fracture context for halite.
Silica and Worker Health — CDC / NIOSH. Why breaking, cutting, grinding, or drilling silica-bearing rock can create hazardous respirable dust.

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Common questions

What is the difference between cleavage and fracture?: Cleavage is repeated breakage along structurally controlled planes of weaker bonding. Fracture describes breakage that does not follow cleavage, such as conchoidal, uneven, splintery, or hackly surfaces.
How do I count mineral cleavage directions?: Count sets of parallel planes, not every visible face. A cubic fragment has three directions because opposite parallel faces belong to the same direction. Rotate the specimen and look for repeated, flat, similarly reflective surfaces.
Which minerals have cleavage at 90 degrees?: Common examples include feldspar with two near-right-angle directions, pyroxene with two directions near 87 and 93 degrees, and halite or galena with three directions at 90 degrees. Angles are approximate in field observations.
Does quartz have cleavage?: Quartz has no useful cleavage. It commonly breaks with curved, shell-like conchoidal fracture. A flat crystal face is a growth surface and should not be mistaken for cleavage.
Should I break a specimen to test cleavage?: Not casually. Prefer an existing broken surface and published data. Do not hammer, chip, crush, or split an unknown, valuable, fragile, fibrous, radioactive, contaminated, or potentially hazardous specimen.

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Mineral Cleavage vs Fracture Chart

Separate look-alikes with cleavage and independent evidence

Verification resources

Common questions