sedimentary

Hag Stone

Perforated Calcarenite or Chert

Hardness: 6-7 (if chert) or 3-4 (if limestone); Color: dark brown, grey, green (due to algae); Luster: dull to earthy; Structure: non-crystalline to micro-crystalline; Feature: natural through-hole.

Hardness: 6-7 (if chert) or 3-4 (if limestone)
Color: dark brown, grey, green (due to algae)
Luster: dull to earthy

Identified July 17, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (if chert) or 3-4 (if limestone); Color: dark brown, grey, green (due to algae); Luster: dull to earthy; Structure: non-crystalline to micro-crystalline; Feature: natural through-hole.

Formation & geological history

Formed primarily in coastal or riverine environments where boring organisms (like piddock clams) or localized water erosion/acidic pockets create a tunnel through the rock over centuries or millennia.

Uses & applications

Historically used as protective amulets in folklore to ward off the 'evil eye', prevent nightmares, and protect livestock. Used today as decorative garden stones or focal pieces in macrame jewelry.

Geological facts

Also known as 'Odin stones', 'Adder stones', or 'fairy stones'. Folklore suggests that looking through the hole allows a person to see into the fairy realm or reveal invisible spirits.

Field identification & locations

Identify by looking for a hole that has been worn completely through by natural forces rather than drilling. Found on beaches, riverbeds, and in areas with ancient sea level changes.