oxides
Jasper
SiO2
- Also known as
- picture jasperocean jaspermookaitebloodstone
- Crystal system
- trigonal
- Hardness
- 6.5–7 on the Mohs scale
- Lustre
- dull
- Colour
- Red, brown, yellow, green, often mottled or patterned
- Where it forms
- Where silica-rich fluid impregnates fine sediment or volcanic ash, incorporating the impurities as it sets. The patterns follow the structures of the material it replaced.
- Chiefly from
- Oregon and Idaho, United StatesWestern AustraliaIndiaMadagascarSouth Africa
Why it is that colour
Iron oxides and clay minerals, present in quantities large enough to make the stone fully opaque — which is the practical difference between jasper and the translucent chalcedonies.
Safety
No hazard from handling.
Where it comes from
Common worldwide. Most named varieties — ocean jasper, mookaite, picture jasper — are single-locality trade names, and some deposits are genuinely small and now exhausted.
Historical use
Worked for tools long before it was worn, and used across the ancient world for seals, amulets and small vessels. Banded iron formation jaspers from Western Australia preserve a record of the oxygenation of the earth's oceans around two billion years ago.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Named in Greek, though ancient usage of the word covered a wider range of stones than it does now, including some green chalcedony. It appears in Exodus among the stones of the high priest's breastplate and in Revelation. The proliferation of individual named jaspers with individual meanings is a modern commercial phenomenon.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
Jasper is where the trade's naming habits are most visible, because "jasper" is not a mineralogical term with a boundary — it is a word for opaque patterned chalcedony, and any new deposit can be given a new name. Ocean jasper, mookaite, bumblebee jasper, kambaba jasper and dozens more are locality trade names, several of them for materials that are not chalcedony at all. Bumblebee "jasper" is a volcanic sediment containing realgar and orpiment, which is to say arsenic.
The scientific interest is real though. The banded iron formations of the Pilbara are jasper, and the alternating red and grey layers record the moment cyanobacteria began putting free oxygen into the sea. They are among the most important rocks on the planet for understanding how the atmosphere came to be breathable.
Identity checked against IMA-CNMNC master list, June 2025.