Pineapple Opal Identification Guide
How to identify pineapple opal, the opalized pseudomorph after ikaite, by its spiky cluster habit and white-to-amber appearance.
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What Pineapple Opal Looks Like
"Pineapple opal" refers to a famous opalized pseudomorph from White Cliffs, Australia, in which radiating clusters of bladed ikaite (or glauberite/aragonite) crystals were replaced by opal, leaving a spiky, pineapple-shaped specimen.
- Color: White, cream, amber, grey, or honey; the rare precious-opal examples flash play-of-color.
- Luster: Waxy to resinous, sometimes pearly.
- Transparency: Translucent to opaque.
- Habit: Distinctive radiating spiky/bladed clusters resembling a pineapple or sea urchin — the defining feature.
Step-by-Step Field ID Checklist
- Examine the overall form. The radiating cluster of bladed "spikes" is the single most diagnostic clue.
- Check the luster. Opal has a soft waxy-to-resinous shine, not the glassy luster of quartz.
- Look for play-of-color. Tilt the piece; precious examples flash, but most pineapple opal is common (potch) opal.
- Test hardness. It scratches glass only with effort and is softer than quartz.
- Note the matrix — often in a sandstone or claystone host from White Cliffs.
Key Diagnostic Tests
- Mohs hardness: ~5.5–6.5, softer than quartz; a steel file marks quartz-imitators differently.
- Streak: White.
- Fracture: Conchoidal; no cleavage.
- Density: ~1.9–2.2 g/cm³ — noticeably light in the hand, a useful opal indicator.
- Acid: No fizz (it is silica; a fizz would indicate aragonite/calcite that was not fully replaced).
Common Look-Alikes and How to Tell Them Apart
- Aragonite or glauberite clusters (unreplaced): These fizz in acid (carbonate) or are softer and water-soluble (sulfate); pineapple opal is inert silica.
- Quartz/chalcedony pseudomorphs: Harder (7) and denser; lack opal's low density and waxy resinous look.
- Cave-grown opal stalactites: Lack the radiating bladed cluster form.
- Synthetic/resin imitations: Lighter and warmer to touch, may smell when hot-pointed, and lack natural matrix.
Where Pineapple Opal Is Found
The classic and essentially exclusive source is the White Cliffs opal field in New South Wales, Australia, where unique geochemistry produced these opalized crystal pseudomorphs. Genuine pineapple opals are rare collector items.
Frequently asked questions
What is pineapple opal?
Pineapple opal is a rare opalized pseudomorph from White Cliffs, Australia, where opal replaced radiating clusters of bladed ikaite/glauberite crystals, creating a spiky, pineapple-shaped specimen.
How can you tell if it's real pineapple opal?
Look for the radiating spiky cluster habit, a waxy-resinous opal luster, low density in the hand (~2 g/cm³), and no fizz in acid; genuine pieces typically come with White Cliffs provenance.
Is pineapple opal valuable?
Yes. It is a rare collector's specimen, and examples that also show precious play-of-color command high prices.
Where does pineapple opal come from?
Almost exclusively from the White Cliffs opal field in New South Wales, Australia.
Pineapple Opal identified by the community
Recent Pineapple Opal specimens identified with Rock Identifier.
