Aventurine Feldspar Identification Guide

What Aventurine Feldspar Looks Like

Aventurine feldspar is the mineralogical name for sunstone — a feldspar (oligoclase, or sometimes labradorite/orthoclase) containing tiny platy inclusions of hematite or copper that produce a warm, metallic aventurescence/schiller. The body color is often orange, reddish-brown, golden, or near-colorless, and tilting the stone reveals glittering coppery-red or golden flashes from the aligned platelets. Luster is vitreous; it is transparent to translucent, frequently with visible flat cleavage surfaces.

Step-by-Step Field ID Checklist

1. Look for metallic spangles — tilt under bright light; aligned coppery/golden flashes (schiller) appear, often concentrated along certain planes.
2. Find feldspar cleavage — look for two flat, reflective cleavage directions meeting at nearly 90 degrees; these flat planes distinguish feldspar from quartz.
3. Note the warm body color — orange to reddish or golden in classic sunstone.
4. Test hardness — about 6–6.5; a steel knife may just scratch it, and it will scratch glass weakly.
5. Check transparency — typically more transparent than quartz aventurine.

Key Diagnostic Tests

• Hardness: 6–6.5 (feldspar), softer than quartz aventurine (7) — a useful separator.
• Cleavage: Two good cleavages at ~90 degrees — diagnostic of feldspar and absent in quartz.
• Aventurescence/schiller: Directional metallic flashes from oriented hematite or native copper platelets.
• Luster: Vitreous, pearly on cleavage planes.
• Streak: White.
• Density: ~2.62–2.65.
• Acid: No reaction.

Common Look-Alikes and How to Tell Them Apart

• Quartz aventurine: Quartz aventurine is harder (7), has no cleavage (conchoidal fracture only), and is usually green with green mica sparkle, whereas aventurine feldspar is softer, shows flat cleavage planes, and has warm coppery-red schiller.
• Goldstone (man-made glass): Uniform dense copper glitter, gas bubbles, no cleavage, softer (~5.5), and an unnaturally even sparkle. Aventurine feldspar has natural directional schiller and feldspar cleavage.
• Other feldspars (moonstone, labradorite): Moonstone shows a floating blue/white adularescence rather than metallic spangles; labradorite shows broad blue-green color flashes (labradorescence). Oregon sunstone (a labradorite) is a specific copper-bearing aventurine feldspar.
• Citrine/orange quartz: Transparent orange but lacks schiller spangles and has no cleavage.

Where Aventurine Feldspar Is Found

Classic aventurine feldspar (sunstone) comes from southern Norway (the original locality), India, Russia, Canada, and Tanzania. The famous Oregon Sunstone (USA) is a copper-bearing labradorite found in basalt flows in eastern Oregon and is renowned for its coppery schiller and color range. Aventurine feldspar typically occurs in igneous rocks such as basalt, syenite, and pegmatite.