Quartz with a feline signature

Tiger’s Eye is a pseudomorph: quartz (SiO₂) replaces fibrous crocidolite while keeping its parallel structure. That micro‑fibrous texture generates the chatoyant band.

Family & variants

Hawk’s Eye is the earlier, blue‑grey stage (less iron staining). Bull’s Eye commonly results from heat treatment producing red/burgundy tones. Tiger iron layers tiger’s eye with hematite and jasper.

Three‑step story

1) Crocidolite grows as blue silky fibers in iron‑rich rocks. 2) Silica‑rich fluids infiltrate and replace the fibers with quartz, preserving alignment. 3) Iron oxides/hydroxides tint the quartz golden‑brown.

Why the “eye” moves

Aligned micro‑fibers act like cylindrical reflectors. The bright band runs perpendicular to fiber direction and moves as the stone or light tilts.

From blue to gold to red

Retained iron state → Hawk’s Eye (blue). Oxidized state → Tiger’s Eye (golden). Natural or applied heating can deepen to Bull’s Eye (red).

Palette

• Honey‑gold — classic warmth.
• Bronze‑brown — high‑contrast bands.
• Blue‑grey — Hawk’s Eye.
• Red/Burgundy — Bull’s Eye (often heat‑treated).

Luster is silky to vitreous. Strong pieces show a sharp, centered eye with minimal “chatter.”

Pattern words

• Ribbon — straight, parallel bands with a single bright eye.
• Feathered — slightly wavy fibers, softer sheen.
• Brecciated — broken and re‑cemented shards (e.g., pietersite).
• Layered — tiger’s eye alternating with hematite/jasper (tiger iron).

Observation tip: Use one tight key light. Rotate until the band snaps on; place the highlight just off‑center to show movement.

Parallel “silk”

Expect parallel micro‑fibers/sub‑grains; the eye runs across them. In brecciated varieties, fibers pivot between fragments, producing swirling eyes.

Color agents

Golden browns from goethite/limonite staining; blue tones from retained crocidolite; reds often show subtle heat effects at edges under magnification.

Treatment clues

Dyed pieces may show color pooling in pits/around drill holes; heat‑red material can display faint surface iridescence and deeper burgundy zones.

Cat’s‑eye chrysoberyl

Sharper, brighter eye in a single‑colored gem; much higher SG (~3.73) and RI (~1.74).

Cat’s‑eye quartz

Chatoyant quartz with rutile/fibrous inclusions; lacks tiger’s eye banded stripes and has different color ranges.

Fiber‑optic glass

Very uniform “eye” that slides smoothly; no natural banding, lower heft, and glassy bubbles/flow lines at 10×.

Bronzite / hypersthene

Bronzy schiller rather than a crisp moving band; different chemistry (pyroxenes) and optics.

Quick checklist

• Golden‑brown stripes with a moving band?
• Spot RI ~1.54, SG ~2.65, conchoidal chips?
• Natural, slightly uneven banding (not factory‑uniform)? → Likely tiger’s eye.

Where it occurs

South Africa (Northern Cape) yields classic golden material; additional sources include Western Australia, Namibia (notably pietersite), and India. Tiger iron is especially associated with South Africa and Australia.

Common uses

Cabochons oriented for a centered eye, beads with stripe continuity, inlay for geometric designs, and sculptural pieces that emphasize ribboning.

Everyday care

• Clean with lukewarm water + mild soap; soft cloth dry.
• Avoid ultrasonics/steam for dyed or fractured pieces.
• Store separately from harder gems to protect the polish.

Jewelry guidance

• Suitable for rings, pendants, bracelets.
• Orient pieces so the eye is strong at normal viewing angles.
• For bead strands, aim for closely matched stripe flow.

On the wheel

• Cut with fibers parallel to the base to maximize the eye.
• Light pressure; keep cool. Pre‑polish 600→1200→3k; finish with cerium oxide or alumina on leather/felt.
• For pietersite, stabilize fractures as needed and record any treatment.

Find the eye

Use a single point light and rock the stone until the band locks in. Note the orientation for photography or study.

Stripe mapping

Trace the fiber/stripe direction on paper beneath the cab—this visualizes why the eye moves as it does.