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Variety · Silicate · of Chalcedony

Jasper

SiO₂

Opaque chalcedony in every color a rock can wear.

Hardness6.5–7
Crystal systemCryptocrystalline
LusterVitreous
Sp. gravity2.58–2.91
ClassSilicate
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Jasper specimen

Jasper — Photo: James St. John · CC BY 2.0

What is Jasper?

Jasper is opaque, microcrystalline quartz — SiO₂ — whose colors come from whatever it swallowed while forming: iron oxides for reds and yellows, chlorite for greens, volcanic ash for scenic 'picture' patterns.

Where agate lets light through, jasper blocks it — that opacity plus conchoidal fracture made it a premier flaking stone. Orbicular, brecciated, and picture jaspers are the lapidary staples.

In one sentence: Opaque quartz in every pattern — from ribbon reds to desert landscapes.

Physical Properties

The full data table is in the panel alongside. Here’s what those numbers actually mean.

Opacity. ~20% foreign material (oxides, clays, ash) makes jasper opaque where agate is clear.

Varieties. Named by pattern — picture, orbicular, brecciated, leopard-skin.

Durability. Pure quartz durability with iron-oxide color — it tumbles and polishes superbly.

What It’s Used For

LapidaryCabochons, beads, and carvings — picture jaspers are landscape paintings in stone.
Historic toolsFlaked for tools where flint was scarce.

How to Identify It

Opaque — light stops at the edgeConchoidal fracture, H ~7White streakAny color, often patterned
Looks like…But differs because…Quick test
AgateTranslucent to transparent — jasper is fully opaqueEdge translucency
FlintUsually gray-black, duller, nodular in chalkColor & context

Where It’s Found

Notable localities for fine specimens:

Biggs Junction, United States Nunkeri, Australia Ashoknagar, IndiaOpen the locality map →