sedimentary

Hag Stone

Perforated Flint or Chert (SiO2)

Hardness: 6.5-7 (Mohs); Color: Tan, grey, or brownish; Luster: Waxy to dull; Structure: Cryptocrystalline; Features: Natural through-hole caused by erosion.

Hardness: 6
Color: Tan, grey, or brownish
Luster: Waxy to dull

Identified May 26, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Tan, grey, or brownish; Luster: Waxy to dull; Structure: Cryptocrystalline; Features: Natural through-hole caused by erosion.

Formation & geological history

Formed as nodules in limestone or chalk beds during the Cretaceous period. The holes are created over thousands of years by the abrasive action of water, sand, or sponges/mollusks boring into softer inclusions.

Uses & applications

Primarily used as a protective talisman in folklore, or in modern jewelry and home decor. Historically used to ward off 'nightmares' or the 'evil eye'.

Geological facts

Also known as Adder Stones, Witch Stones, or Odin Stones. In many cultures, looking through the hole is said to reveal the 'invisible' or faerie realm.

Field identification & locations

Identify by finding a rock with a naturally occurring hole that goes all the way through. Most commonly found on beaches or in riverbeds where water erosion is high.