How to clean it
Warm soapy water and a soft cloth. Avoid prolonged soaking.
Banded reddish brown and white
Sardonyx
The birthstone for August.
Is Sardonyx a birthstone?
Yes. Sardonyx is the traditional birthstone for August.
Properties
Composition
Banded chalcedony — alternating layers of sard and onyx
Hardness (Mohs)
6.5–7
Crystal system
Trigonal
Colour
Banded reddish brown and white
Mined in
India, Brazil, Germany, Czech Republic
Worth knowing
Its parallel banding made it the preferred material for cameos — carvers cut through a pale layer to reveal a dark one beneath.
History
The Romans carved seals from it because hot wax does not stick to its surface.
Practical
Caring for Sardonyx
How to tell it is real
Banded agate is often dyed to imitate sardonyx. Natural banding is irregular; dyed banding is too even and the colour sits in the porous layers.
One general rule covers most mistakes: never store stones loose together. Diamond at 10 on the Mohs scale scratches everything else you own, and it does not need much contact to do it.
What that hardness means in practice
Softer than household dust. Better in earrings or a pendant than in a ring, where it takes constant knocks.
Traditional associations
Sardonyx is traditionally linked to steadiness, discipline and durable commitments. In chakra systems it is placed at the Root, and in elemental correspondence it is assigned to Earth.
These are cultural associations recorded across various traditions, not claims about physical effects. The composition and hardness above are measurable; this paragraph is folklore, and worth reading as such.
Questions
What is Sardonyx made of?
Banded chalcedony — alternating layers of sard and onyx, crystallising in the trigonal system.
Which month is Sardonyx the birthstone for?
August.
Where does Sardonyx come from?
India, Brazil, Germany, Czech Republic.
How do I clean Sardonyx?
Warm soapy water and a soft cloth. Avoid prolonged soaking.
How can I tell if Sardonyx is real?
Banded agate is often dyed to imitate sardonyx. Natural banding is irregular; dyed banding is too even and the colour sits in the porous layers.
Can I wear it every day?
At 6.5–7 on the Mohs scale, not in a ring. Keep it to pieces that take fewer knocks.