Stone Beads: Santa Rita Green and Purple

April 11, 2012

This Moon I have been carving stone beads from pebbles that I collected in Sycamore Canyon and other canyons in the Santa Rita Mountains.  Eventually I want to make enough for a necklace.   I have a fairly efficient system for cutting the blanks, drilling holes, carving, hand-sanding, and polishing.  Even so, it’s a slow process, averaging one finished bead a day.  It’s fun to watch the strand grow.  It’s acquired a “Green and Purple” color theme, partly inspired by the rocks themselves and partly by the endemic Santa Rita prickly pear cactus (Opuntia santa-rita), which is pale grayish-green in the summer and turns a distinctive mauve color in winter.  Three of the new beads are shown below.  All are slightly softer than agate and take a soft polish rather than a mirror shine, even when diamond powder is used.  At left is a bead made of diopside (a green pyroxene) and calcite, sometimes called “calcsilicate rock”.  It is from a skarn, a special type of contact metamorphic rock that is produced when granitic magma intrudes limestone or marble.  In the center is a volcanic rock that has been extensively altered to clays and hematite, so its original composition is unknown (it’s from the outcrop pictured below).  At right is an altered and slightly metamorphosed rhyolite; the pistachio-colored mineral is epidote and the dark green veins are diopside.  Rhyolite is a light colored volcanic rock which is equivalent to granite in composition; it is the main rock type of the Santa Ritas but comes in a wide variety of colors and textures.

Three Handmade Stone Beads

Three Handmade Stone Beads

Here’s an outcrop of altered and weathered purple volcanic rock with a vein of epidote (yellowish-green), chlorite, and diopside (bluish-green) exposed on a weathered surface.

Green and Purple Outcrop

Green and Purple Outcrop

Here’s the Santa Rita prickly pear in midwinter, growing wild in Chino Canyon.  The green prickly pear in the center of the photo is a more common species, Opuntia engelmanii.

Santa Rita Prickly Pear in Winter

Santa Rita Prickly Pear in Winter

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2 Responses to “Stone Beads: Santa Rita Green and Purple”

  1. judithornot said

    Love the beads! I have a polished piece of rhyolite I enjoy carrying in my pocket. :-)

  2. ironwing said

    Most commercially-available “gem” rhyolite is silicified (has secondary chalcedony filling the voids) so it’s hard, like agate, and takes a high polish. For example, there’s a popular Australian variety that is blotched with various shades of green and brown, with spots of pink or purplish chalcedony.
    “Fresh” or unaltered rhyolite also polishes very well (a few of my beads are of that type but I haven’t posted photos of them yet).

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