Pinacoid

Definitions

  • Webster's Revised Unabridged Dictionary
    • n Pinacoid (Crystallog) A plane parallel to two of the crystalline axes.
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Century Dictionary and Cyclopedia
    • n pinacoid In crystallography, a plane parallel to two of the crystallographic axes: as, the basal pinacoid, or base parallel to the lateral axes. The macropinacoid and brachypinacoid are planes in the orthorhombic system parallel to the vertical axis and the longer or shorter lateral axis respectively; similarly the orthopinacoid and clinopinacoid, in the monoclinic system, are parallel to the vertical axis and the orthodiagonal or clinodiagonal axis respectively.
    • n pinacoid Some authors extend the use of this term to embrace any form which has but two parallel faces; according to this usage, all the possible faces of a holosymmetric triclinic crystal are called pinacoids.
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Etymology

Webster's Revised Unabridged Dictionary
Gr. , , a tablet + -oid,

Usage

In literature:

The cleavage is perfect parallel to the basal pinacoid, and less marked parallel to the prism.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 5" by Various
Acute rhombohedra in combination with the basal pinacoid are also frequent, giving crystals of octahedral aspect.
"Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 7" by Various
There is an imperfect cleavage parallel to the basal pinacoid, and the fracture is conchoidal.
"Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 2" by Various
All the forms, except the prisms and basal pinacoid, are sphenoids.
"Encyclopaedia Britannica, 11th Edition, Volume 7, Slice 7" by Various
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