Mariposite Identification Guide

What Mariposite Looks Like

Mariposite is a rock name (and an informal mineral name) for a green, chromium-rich variety of the white mica fuchsite/muscovite, usually intergrown with quartz and carbonate (the rock is sometimes called mariposite rock or green schist). The green mica is scattered through a pale matrix, giving a sparkling, mottled green-and-white or green-and-cream appearance with a silky, schistose sheen.

• Color: apple-green to bluish-green mica in white, cream, or gray quartz-carbonate matrix
• Luster: pearly to silky (mica); the rock sparkles
• Transparency: opaque
• Texture: foliated/schistose, with flaky reflective mica

Step-by-Step Field ID Checklist

1. Look for sparkle - reflective green mica flakes catching the light is the key clue.
2. Check softness of the green mineral - the mica is soft and flaky (Mohs ~2-3), peeling in thin sheets.
3. Note the two-part texture - soft green mica in a harder quartz-carbonate host.
4. Test the matrix with acid - carbonate-rich zones fizz; quartz-rich zones do not.
5. Check the streak - white to pale green.

Key Diagnostic Tests

• Mohs hardness: the green mica is soft (~2-3); the quartz matrix is hard (7), so the rock has mixed hardness.
• Streak: white to very pale green.
• Cleavage: the mica shows perfect basal (one-direction) cleavage, peeling into flexible flakes.
• Acid: carbonate component effervesces in dilute HCl.
• Specific gravity: moderate, around 2.7-2.9.

Common Look-Alikes and How to Tell Them Apart

• Fuchsite/aventurine quartz (green): mariposite is the rock; massive fuchsite quartzite can look similar but is harder throughout. Mariposite typically has visible carbonate that fizzes.
• Verdite/green serpentine: serpentine is greasier, more uniform, and lacks sparkling mica flakes.
• Green marble: fizzes strongly all over and lacks the flaky reflective mica sparkle.
• Mariposite imitations (dyed howlite/quartz): look for natural flaky mica texture rather than uniform dyed color.

Where It Is Typically Found

Mariposite is named for Mariposa County, California, where it occurs in the Mother Lode gold belt - notably it is often associated with gold-bearing quartz-carbonate veins in altered serpentinite. Similar chromian-mica rocks occur in other gold districts and ophiolite belts worldwide.