Judging quality
Look for fine, tight, well-defined banding and honest color. Bright turquoise, magenta and neon agate slices are dyed; natural colors are earth tones, greys, blues and translucent whites.
Chalcedony
Agate
Banded chalcedony, formed as silica-rich fluid seeped in layers into volcanic cavities. Every agate is a cross-section of its own slow filling, which is why no two slices repeat.
Care
Very durable. Wash with soap and water; polished faces can be re-buffed.
History & lore
Idar-Oberstein in Germany has cut agate continuously since the 1400s and gave the world much of modern lapidary technique.
Cultural history, recorded as tradition rather than as medical or scientific claim.
Common questions about Agate
- What is Agate?
- Banded chalcedony, formed as silica-rich fluid seeped in layers into volcanic cavities. Every agate is a cross-section of its own slow filling, which is why no two slices repeat.
- How hard is Agate and what is it made of?
- Agate is a Chalcedony-family mineral with the composition SiO2. It crystallizes in the trigonal system and rates 6.5-7 on the Mohs hardness scale. It occurs in banded, grey, blue, red.
- Where does Agate come from?
- Notable localities for Agate include Brazil, Botswana, Mexico, Germany (Idar-Oberstein).
- How do you tell good Agate from filler?
- Look for fine, tight, well-defined banding and honest color. Bright turquoise, magenta and neon agate slices are dyed; natural colors are earth tones, greys, blues and translucent whites.
- How do you care for Agate?
- Very durable. Wash with soap and water; polished faces can be re-buffed.
See it in person
Photographs only go so far
Both rooms are open six days a week, and there is always someone happy to pull pieces out of the case so you can compare them under the light.