Peridotite with chrome diopside and spinel in volcanic basalt

Locale: San Carlos, Arizona

Approx dimensions: 3 x 2 x 1"

Approx weight: 212g

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 high-quality material from San Carlos, Arizona, has peridotite containing olivine (light yellow-green), chrome diopside (vivid green), and spinel (deep forest green), creating beautiful tones.

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!