GEOLOGY
PHYSICAL GEOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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TRUE
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FALSE
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Either A or B
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None of the above
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Detailed explanation-1: -Some minerals tend to cleave along planes at various fixed orientations, some do not cleave at all (they only fracture). Minerals that have cleavage can also fracture along surfaces that are not parallel to their cleavage planes.
Detailed explanation-2: -A mineral can have both cleavage and fracture, and some have either one or the other. Quartz has no cleavage, only fracture. Calcite has no fracture, only cleavage. Feldspar has both.
Detailed explanation-3: -When a mineral fractures along a cleavage plane, what does this suggest about the crystal structure of the mineral? The crystal structure contains planes along which chemical bonding is much weaker than other directions.
Detailed explanation-4: -Basal or pinacoidal cleavage occurs parallel to the base of a crystal. This orientation is given by the 001 plane in the crystal lattice (see the Miller indexes page in Wikipedia), and is the same as the 0001 plane in Bravais-Miller indexes, which are often used for rhombohedral and hexagonal crystals.