• A rough irregular chunk of dark gray porous volcanic basalt pocked with bubble holes. There is a patch of gemmy peridotite in the center and some lower quality peridotite in smaller patches on the edges
  • Detail view of the patch of desaturated yellow-green peridotite crystals, some with dark green spinel and diopside crystals mixed in.
  • And irregular side of the piece with large bubble holes in the volcanic rock and peridotite on the top and right sides.
  • A side of the piece with focus on the gemmy patch of peridotite primarily composed of olivine.
  • Looking down the point of the piece at the gemmy olivine patch with larger translucent crystals.
  • A triangular face of the piece covered in peridotite, with two more patched of peridotite on the right-hand face
  • A rectangular side of the piece with low quality desaturated peridotite on the end and a large bubble hole structure.
  • Scale image of the piece on a measuring mat, measuring about two and a half inches long with a longer point, and bit over an inch and a half wide.
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Peridotite in volcanic basalt

Peridotite in volcanic basalt

$22.00 USD
$22.00 USD
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Locale: Arizona

Approx dimensions: 2.5 x 1.5 x 1.5"

Approx weight: 175g

 

While this material is commonly called peridot in (or ‘on’) basalt, it is actually more complex. It would be more accurately called a peridotite xenolith in basalt. Peridot is the gem-quality version of the mineral olivine, which is common in our Earth’s upper mantle—and even in space. In comparison, peridotite is a combination of several types of minerals that primarily features olivine, but can also contain spinel, garnet, diopside, and other igneous minerals. This medium-quality material from Arizona has peridotite containing yellow-green olivine, which can be a duller desaturated color when lower quality as seen in some areas on this piece. There are some irregular crystals of chrome diopside (vivid green) and spinel (deep forest green) in the mix.

Xenolith means there are pockets of ‘foreign’ material, peridotite, included within the igneous rock, basalt. This is what's called vesicular basalt, referring to the classic 'volcanic rock' style of basalt full of cavities left behind by gas bubbles. The peridotite would have formed in the upper mantle but pieces of it became entrapped in magma during the eruption that transported it to the earth’s surface.

** Brittle warning! This material has the tendency to be crumbly, shedding pieces when handled. I find it to be a beautiful accent rock for my garden and do keep some pieces outdoors despite this risk. Just keep it out of direct sunlight and the elements!

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