igneous
Tumbled blue-green stone, likely amazonite-bearing granite or microcline
Amazonite (green microcline, KAlSi₃O₈) in a granitic host; exact identification uncertain from photo
AI-generated identification · may be incorrectBlue-green to gray, opaque, dull-to-waxy tumbled surface with dark mineral streaks/inclusions. Microcline hardness is about 6–6.5 Mohs, with two cleavages at nearly 90°; specific gravity about 2.55–2.63. No visible crystal faces remain after tumbling.
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Physical properties
Blue-green to gray, opaque, dull-to-waxy tumbled surface with dark mineral streaks/inclusions. Microcline hardness is about 6–6.5 Mohs, with two cleavages at nearly 90°; specific gravity about 2.55–2.63. No visible crystal faces remain after tumbling.
Formation & geological history
Likely formed in a potassium-rich granite or pegmatite as amazonite microcline, commonly hundreds of millions to billions of years old. The rounded shape is human-tumbled and polished by abrasion.
Uses & applications
Used as an ornamental and lapidary stone, in cabochons, carvings, beads, and inexpensive polished specimens.
Geological facts
Amazonite’s blue-green color is related to trace lead and water-related defects in microcline’s crystal structure. Similar-looking stones include chrysocolla, turquoise, serpentine, and dyed rocks.
Field identification & locations
The specimen is consistent with commercial tumbled amazonite, but visual identification is not definitive. Near 38.6°N, 84.3°W (northern Kentucky), local bedrock is mainly sedimentary, so a purchased or transported specimen is more likely than locally formed amazonite. A hardness test and streak test can help; amazonite leaves a white streak and resists scratching by steel.
