pinacoid


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pinacoid

[′pin·ə‚kȯid]
(crystallography)
An open crystal form that comprises two parallel faces.
References in periodicals archive ?
The micrographs were horizontally aligned with the basal pinacoid and vertically aligned parallel to the c-axis of the corundum host.
Habit 5 occurs as large apatite-(CaF) crystals with prism faces as long or longer than the basal pinacoids.
A Vietnamese locality for loose, gemmy, yellow-orange crystals of heliodor beryl may be in the offing; there were single examples and a few very small lots of these crystals scattered about the Holiday Inn show, but the best I noted were two sharp hexagonal prisms with simple pinacoid terminations, 4 and 10 cm long, in the Pala International room.
Most stephanite crystals from the Las Chispas mine are short, thick, pseudo-hexagonal prisms formed by a combination of the prism and pinacoid, exceptionally to 12 cm across.
The Schneckenstein crystals generally have a large well-developed basal pinacoid that is not seen on Ouro Preto crystals.
However, in a specimen collected in December 2002, a mixture of galena and calcite forms a pseudomorph after three parallel hexagonal crystals (with prism and pinacoid faces), to 1 + 3 cm, of an unknown mineral on a pink manganocalcite crystal.
These swanky crystals are mirror-faced, impeccably sharp, and deep green in their inner zones but nearly colorless in thin outer zones rimming them all around; some have little blossoms of white albite crystals clinging to the pinacoid faces.
Subordinate {101} faces are usually present, and the {001} pinacoid faces tend to have a parqueted surface (Ottens, 2003).
Some of these crystals have odd white fringes around the basal pinacoid faces on both ends, and in one InnSuites room (that of Javed Iqbal of Hi-Tech, hitechfp@yahoo.
The vast majority of the mimetite crystals are simple, blocky, hexagonal prisms with large, smooth pinacoid faces.
This time there were hopeful signs: Dudley Blauwet of Mountain Minerals International had a couple of very nice miniature specimens wherein the vesuvianite crystals are terminated on both ends by shiny pinacoid faces, and Rob Lavinsky showed me three just-acquired thumbnails with truly first-rate aesthetics: they are rich brownish purple (more brown than in earlier cases), doubly terminated vesuvianite crystals to 2 cm in crisp little groups with milky white calcite crystals.
Dr Dietmar Schwarz (AIGS Lab, Bangkok) illustrated the many physical and chemical distinctions of Colombian emeralds as compared to those from other sources, notably their high Cr+V content and diagnostic three-phase inclusions, as well as characteristic growth features such as first-order prisms and pinacoids.