In my March 31, 2017 post concerning a distinctive granite, I showed an orthoclase crystal with twinning, which occurs when two separate crystals of the same substance share some of the same crystal lattice. Instead of a normal single crystal, the crystalline structure appears doubled.
In this new post, I show some other common examples from my personal collection of twinned crystals. They are aragonite, pyrite, gypsum, quartz, and staurolite.
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| aragonite (40 mm length) |
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| gypsum (37 mm length) |
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| pyrite cubes (47 mm length) |
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| quartz (47 mm length) |
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| staurolite (18 mm length) |
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pseudomorph of staurolite (40 mm)
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| pseudomorph of staurolite (40 mm length) |
pseudomorphs are formed
when a mineral is replaced
by a foreign substance
Single crystals are materials in which the entire sample has a continuous and unbroken crystal lattice to the edges of the sample with no grain boundaries. The lack of defects associated with grain boundaries can impart unique properties to single crystals, pure element single crystals
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