W041 / Oregon

Polka Dot agate

Trade-named spotted siliceous material

An agate name does not guarantee an agate structure. Polka Dot material can be finely crystalline silica with conspicuous dark spots; true banded agate also occurs with it.

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Spotted siliceous Polka Dot specimen from a source-labelled Oregon example
Source-labelled Polka Dot material; an example, not a provenance test.

James St. John, 2025 · CC BY 4.0 · Responsive resizing; no substantive image edits.

Photographer’s locality attribution is retained. It does not authenticate another visually similar slab.

Image source and provenance · License

What it is

Trade-named spotted siliceous material

What to look for

Compare rounded brown, red, yellow or dark spots against a pale silica ground. The pattern is a comparison clue, not proof of an Oregon source.

At the cutting bench

Spot placement and fractures determine the best polished face. Do not assume every portion of the host material cuts or polishes equally.

Under the loupe

Compare other spotted jaspers and siliceous rocks. Keep the trade name separate from the observed texture, and retain any mine label.

Source & collecting access

Historical collecting and a source-labelled 2025 photograph do not establish present ownership, commercial output or permission to collect. Current access is UNKNOWN.

Status checked 2026-10-03

The market notebook

No verified realized-price range was established for this entry. Asking prices and sold labels are not interchangeable.

Market researched 2026-10-03

Open the field notes

Formation & evidence

DOGAMI’s historical account describes spotted fine-quartz material near Pony Creek. A recent source-labelled example is described by its photographer as finely crystalline siliceous rock with iron-oxide spherulites, without the concentric banding expected of agate. Neither account establishes the identity of every traded piece.

Collecting & trade context

The historic description also uses St. Stephen stone. Preserve that wording on old labels rather than treating it as a modern species name.

Reading an old label

Preserve labels, dates, wrapping and associated pieces. Visual resemblance, material identity, locality attribution and documented provenance are separate conclusions.

What we know—and what we don’t

Visual resemblance can narrow a comparison. Material identity, locality attribution and documented provenance need separate evidence.

C&C Reference Collection

Source-labelled reference examples are linked below. Images without explicit reuse permission are not reproduced.

Sources & Further Reading
  1. DOGAMI: The Gem Minerals of Oregon, Bulletin 7

    Historical description; not present access evidence.

  2. James St. John: source-labelled Polka Dot material

    Photographer’s primary specimen description; one example is not a universal material diagnosis.

Historic locality information is not current collecting permission. For cutting, use suitable dust controls and material-specific safety guidance.