Jelly Opal Identification Guide

What Jelly Opal Looks Like

Jelly opal is a transparent to translucent opal with a gelatinous, watery body and little to no opaque potch. It may be colorless, bluish, or pale, and the best stones show subtle internal flashes of play-of-color floating within the clear gel.

• Color: near-colorless, pale blue, grey, amber; may show faint play-of-color
• Luster: vitreous to slightly resinous/waxy
• Transparency: transparent to translucent — the defining 'jelly' look
• Form: amorphous (non-crystalline) hydrated silica; massive, nodular, or in seams

Step-by-Step Field-ID Checklist

1. Note the clear, gel-like body — you can often see into the stone, sometimes with a watery depth.
2. Tilt for play-of-color. Any drifting spectral flashes inside the clear body indicate precious jelly opal.
3. Hardness test: opal is soft, Mohs 5.5–6.5 — it will NOT scratch glass reliably and is easily scratched itself. Test gently.
4. Check weight. Opal is light (SG ~1.9–2.2), noticeably lighter than glass and quartz.
5. Watch for hydrophane behavior. Some jelly opal absorbs water and changes transparency when wet (test cautiously; can be damaging).
6. Look for conchoidal fracture and no cleavage.

Key Diagnostic Tests

• Mohs hardness: 5.5–6.5 (soft for a gem)
• Streak: white
• Fracture: conchoidal; no cleavage (amorphous)
• Specific gravity: ~1.98–2.20 — distinctly low/light, a strong clue
• No acid reaction; not magnetic
• UV fluorescence: many opals fluoresce green/white under UV, aiding ID

Common Look-Alikes and How to Tell Them Apart

• Moonstone: crystalline feldspar with cleavage and adularescence (a billowy sheen), harder (6–6.5) and denser; jelly opal is amorphous, lighter, and gel-like.
• Glass: harder than opal in many cases and denser (SG ~2.5); shows bubbles and lacks true play-of-color (manmade 'opalite' glass shows a flat blue/orange flash, not drifting spectral colors).
• Girasol/rose quartz girasol: quartz is harder (7) and denser; jelly opal is softer and lighter.
• Chalcedony: translucent but harder (7) and microcrystalline, no opal play-of-color.
• Opalite (manmade): a milky glass with a single bluish glow and orange transmission; lacks the random spectral play and is denser than true opal.

Where Jelly Opal Is Found

Jelly and crystal opal come from Australia (Lightning Ridge, Coober Pedy), Ethiopia (Wollo — much of it hydrophane), Brazil, and Mexico (water opal). Opal forms from silica-laden groundwater deposited in cavities, seams, and weathered host rocks at low temperatures.