Spiderweb Jasper
Silicon dioxide (SiO2), variety of chalcedony/microcrystalline quartz
A jasper crossed by fine dark veins forming a spiderweb-like network, often a brecciated stone cemented by darker matrix.
- Mohs hardness
- 6.5-7
- Color
- Tan, cream, red, brown, or gray with dark web-like veining
- Type
- mineral
Got a rock like this?
Identify any rock from a photo, free.
Overview
Spiderweb Jasper is a variety of jasper distinguished by a network of fine, dark veins that crisscross the stone like a spider's web. The body color varies widely, tan, cream, red, brown, or gray, while the contrasting webbing is formed by darker mineral-filled fractures.
It is an opaque microcrystalline quartz (chalcedony), and many specimens are brecciated, with fragments held together by a darker silica or iron-oxide matrix that produces the web pattern.
The name is used as a trade term for several jaspers worldwide that share this distinctive veined appearance, prized by lapidaries for its graphic contrast.
Formation & geology
Spiderweb Jasper forms when an existing jasper is fractured and the cracks are later filled by silica-rich or iron-bearing solutions that deposit darker material along the breaks. This creates the characteristic network of contrasting veins.
In brecciated examples, the host jasper broke into angular fragments that were then re-cemented, with the darker cement outlining each piece to form the web. The whole mass slowly hardened into a dense, polishable stone.
It occurs in volcanic and sedimentary terrains worldwide wherever jasper has been fractured and re-mineralized.
How to identify it
Identify Spiderweb Jasper by its network of thin, dark veins forming a web across a lighter body. It is opaque, hard (6.5-7), scratches glass, resists a steel knife, and shows a white streak with a waxy-to-glassy polish.
The webbing is a structural feature filling fractures, distinguishing it from dendritic agate, where the dark branches are tree-like mineral growths within translucent chalcedony rather than crack-fillings in opaque jasper.
It does not fizz in acid, separating it from veined marbles. Compare with brecciated jasper, which has angular fragments; spiderweb jasper emphasizes a finer, continuous web of veins.
Uses & significance
Spiderweb Jasper is used for cabochons, beads, pendants, and tumbled stones, valued for the strong graphic contrast between body and webbing. Its hardness makes it durable for rings and everyday jewelry.
Lapidaries seek pieces with crisp, well-defined webs and pleasing body color for striking cabochons.
Metaphysically it is associated with grounding, protection, and stability, regarded by enthusiasts as a calming, connective stone. These are spiritual associations rather than scientific facts.
Frequently asked questions
What makes the web pattern in Spiderweb Jasper?
Fine fractures in the jasper were filled by darker silica or iron-bearing minerals, creating the contrasting web-like veining.
Is Spiderweb Jasper the same as turquoise with spiderweb matrix?
No. Spiderweb turquoise is a separate copper mineral; spiderweb jasper is quartz-based and harder, with its own naturally veined pattern.
How is it different from dendritic agate?
Dendritic agate has tree-like mineral growths in translucent chalcedony, while spiderweb jasper has crack-filling veins in opaque jasper.
Is Spiderweb Jasper durable?
Yes. At Mohs 6.5-7 it is suitable for rings, pendants, and daily-wear jewelry.
Spiderweb Jasper guides
In-depth guides for identifying, valuing, and understanding Spiderweb Jasper.
Spiderweb Jasper identified by the community
Real specimens identified with Rock Identifier.
