Peach Moonstone Identification Guide

What Peach Moonstone Looks Like

Peach moonstone is a potassium feldspar (orthoclase/microcline) or sodium-rich plagioclase variety showing a warm peach to apricot body color with a soft, floating internal glow called adularescence. The sheen looks like moonlight drifting beneath the surface and shifts as you tilt the stone. Luster is vitreous to slightly pearly, and clarity ranges from translucent to nearly opaque. Cabochons are the usual cut because the billowy sheen needs a domed surface to show.

Quick visual cues

• Warm peach/cream body color with a milky-to-bluish floating sheen
• Adularescence that moves when the stone is rocked
• Pearly-to-glassy luster
• Sometimes a faint sheen of tiny included flecks (similar to sunstone) in peach material

Step-by-Step Field ID Checklist

1. Rock the stone under a single light and watch for the soft, moving glow rising from within — the signature of moonstone.
2. Inspect the body color: an even peach to champagne tone, not a banded or dyed look.
3. Test hardness: feldspar is 6-6.5 Mohs; it scratches glass but is scratched by quartz and topaz.
4. Look for cleavage. Feldspar shows two directions of cleavage meeting near 90°; broken edges look stepped and flat.
5. Check the streak: white.
6. Look for a faint sheen line rather than a sharp cat's-eye; true moonstone glow is diffuse.

Key Diagnostic Tests

• Mohs hardness: 6-6.5.
• Streak: white.
• Cleavage: two good cleavages intersecting at roughly 90° (perthitic lamellae cause the sheen).
• Specific gravity: ~2.55-2.63, light in the hand.
• Optics: biaxial, with adularescence from light scattering off internal feldspar layering.
• Acid: no reaction (distinguishes from carbonate imitations).

Common Look-Alikes and How to Tell Them Apart

• Peach chalcedony/agate: harder (7), no adularescent sheen, conchoidal fracture, no cleavage.
• Opalite (glass): shows a flat, uniform blue-white glow and gas bubbles under magnification; moonstone's sheen moves and feldspar has cleavage.
• Peach sunstone: sunstone shows metallic copper/hematite platelet flashes (aventurescence) rather than a soft floating glow, though some peach moonstone is borderline.
• Dyed peach quartz: color concentrates in cracks; quartz lacks cleavage and adularescence.
• Cultured opal/plastic: lighter, warm to the touch, and shows no true feldspar cleavage.

The decisive combination is adularescent floating sheen + two feldspar cleavages + ~2.6 SG + no acid reaction.

Where Peach Moonstone Is Found

Peach and cream moonstone come chiefly from India, Sri Lanka, Madagascar, Tanzania, and Myanmar, with additional material from Brazil and the United States. It forms in pegmatites and in feldspar-rich igneous and metamorphic rocks, where slow cooling allows the fine intergrowths that create the moonlight effect.