Jasper, agate… or both?

“Jasper” in lapidary shorthand means colorful, opaque microcrystalline quartz. Ocean jasper toggles between jaspery (opaque) and agate‑like (translucent bands), often in the same piece. The orbs are concentric chalcedony growths, sometimes ringed by fine agate.

Trade name with a real place

Ocean jasper is closely tied to the northwest coast of Madagascar. The original material became known for being collected from cliff and tide‑zone exposures—hence the sea‑leaning name. You may also see location nicknames like Kabamby (often green‑yellow) and Marovato (multi‑color orbs).

Volcanic canvas

The host rock began as silica‑rich volcanic flows/tuffs (rhyolitic). As hot fluids circulated, they delivered silica that permeated and replaced the rock, laying the groundwork for chalcedony/agate growth.

Seed, ring, repeat

Minute nuclei—tiny cavities or mineral specks—kick off radial chalcedony growth. Chemistry pulses create concentric rings of different colors, sometimes bordered by translucent agate. Neighboring orbs bump and overlap like raindrops on a pond.

Glitter finish

Where cavities stayed open, late silica lined them with drusy quartz. Those are the little glittering pockets that catch the light when you tilt a cab—geology’s equivalent of sequins.

Palette

• Greens — sage to deep forest.
• Yellows/ochres — common in Kabamby material.
• Reds — iron‑rich rings and fields.
• Pinks/mauves — soft pastels in many orbs.
• White/cream — agate rims and quartz heals.
• Charcoal/black — contrast bands or matrix streaks.

Most pieces are opaque with translucent windows in thin agate bands or around drusy cavities.

Pattern words

• Orbicules / “eyes” — round targets, often with multi‑color rings.
• Ocelli — bull’s‑eye orbs with a contrasting center point.
• Banded agate rims — thin translucent halos outlining orbs.
• Drusy pockets — tiny quartz‑lined caves (sparkle alert).
• Montage fields — overlapping orbs like mosaic tile.

Photo tip: Side‑light at ~30° makes the agate halos glow and drusy glitter without washing out the pastels.

Radial micro‑fibres

At 10×, many orbs show radial chalcedony structure—tiny fibres shooting outward from a center. Between rings, color shifts with minute changes in inclusion density.

Agate halos

Look for translucent, finely banded rims around orbs. Tilt the slab and you’ll see light creep through those halos like sunrise around islands.

Drusy detail

Drusy pockets are lined with micro‑quartz crystals. Under raking light they sparkle; under magnification you’ll spot sharp, tiny points arranged like sugar on a doughnut. (Tasty metaphor, inedible stone.)

Leopard “jasper” (orbicular rhyolite)

Leopardite’s rhyolite matrix is feldspar‑rich and lacks agate halos/drusy quartz typical of ocean jasper. Under magnification, orbs look more like devitrified spherulites with oxide rims than chalcedony rings.

Poppy/orbicular jaspers (various locales)

Similar circular motifs, but many show solid jasper orbs with less translucency and fewer drusy pockets. Ocean jasper often mixes opaque fields with translucent edges.

Dyed composites

Uniform neon colors and repeating patterns suggest resin‑bound or dyed stone. Natural ocean jasper shows organic variation, subtle halos, and non‑repeating orbs.

Orbicular rhyolite vs. orbicular chalcedony

Quick tell: agate rims + drusy lean toward ocean jasper (chalcedony); granular feldspar groundmass without translucent bands leans rhyolite.

Checklist

• Concentric “eyes” with translucent halos.
• Occasional drusy quartz pockets.
• Pastel‑to‑earth palette with gentle, non‑uniform shifts.

At‑home peek

Back‑light a thin edge: agate halos glow; jaspery fields stay opaque. A 10× loupe reveals fine concentric banding rather than painted‑on color.

Coastal Madagascar

Northwestern Madagascar hosts silicified volcanic rocks along the coast. In places the jasper/agate exposures meet the sea, and material has historically been collected at low tide from cliffs and boulders.

Named pockets

Material labeled Kabamby often leans green‑yellow with bold orbs; Marovato is known for multi‑color orbs, pinks, and whites with drusy. Exact looks vary layer by layer—nature doesn’t copy‑paste.

Everyday handling

• Quartz hardness (~7) = good durability.
• Edges can chip if dropped; treat like any polished chalcedony.

Cleaning

• Lukewarm water + mild soap + soft cloth/brush; rinse and dry.
• Avoid aggressive acids/bleach that can haze surfaces or react with iron skins.

Lapidary tips

• Orient slabs so orbs traverse the dome; include a drusy pocket near (not on) the apex for sparkle.
• Take your time on pre‑polish to keep halos crisp; finish with cerium/diamond on soft pads.
• Stabilization is rarely needed; fill only if a cavity compromises structure.

Halo glow

Hold a thin edge to a flashlight: many “eyes” reveal glowing translucent rings—instant agate reveal inside the jasper.

Spot the sparkle

Rock the piece under raking light and watch drusy pockets twinkle. It’s subtle, classy glitter—the mineral version of starry seas.