Oregon Thunderegg Value Guide

Designated as the Oregon State Rock in 1965, these lithophysal geodes are prized for their unique formation within ancient rhyolitic lava flows. Collectors value them for their rich history, including Native American legends that describe them as weapons hurled by Thunder Spirits from Mount Hood.

What affects the value of Oregon Thunderegg?

• The complexity and color of the agate core, with vibrant patterns or rare inclusions commanding higher interest.
• The quality of the polish on the cut face, which should be smooth and free of deep scratches or chips.
• The size and symmetry of the specimen, with well-defined 'star' shapes being particularly desirable for 1960-1980 era pieces.
• The overall condition of the rhyolite shell, ensuring it remains intact and provides a solid frame for the inner gemstone.

How to Identify Oregon Thunderegg?

• Look for a distinctive knobby, spherical rhyolitic exterior shell that resembles a rough stone or dried mud.
• Verify the interior core consists of polished agate or chalcedony, often displaying star-shaped patterns.
• Check for the specific geological characteristics of United States origin, particularly those sourced from Oregon's volcanic regions.
• Examine the specimen for a cut and polished face that reveals the contrast between the outer matrix and the translucent inner minerals.

History of Oregon Thunderegg

Designated as the Oregon State Rock in 1965, these geological wonders formed in gas cavities within rhyolitic lava flows millions of years ago. Native American legend claimed these were weapons hurled by the Thunder Spirits living atop Mount Hood and Mount Jefferson.