Tiger eye - www.Crystals.eu

Tiger eye

Tiger’s Eye • chatoyant quartz — pseudomorph after crocidolite (riebeckite) fibers Crystal system: Trigonal (quartz) • Habit: micro‑fibrous aggregate producing a moving “cat’s‑eye” band Mohs: 7 • SG: ~2.64–2.71 • Luster: silky to vitreous Colors: honey → bronze‑brown; variants: Hawk’s Eye (blue‑grey), Bull’s Eye (red) Also seen as: Tiger iron (tiger’s eye + red jasper + hematite), Pietersite (brecciated chatoyant quartz)

Tiger’s Eye — Liquid Light in Stone

Tiger’s Eye is quartz that has replaced silky crocidolite fibers, preserving their alignment as microscopic “silk.” When cut correctly, light concentrates into a moving band—the feline flash known as chatoyancy. Honey to bronze hues arise from iron oxides; retain more blue for Hawk’s Eye, or deepen to red tones in Bull’s Eye.

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What it is
Chatoyant quartz formed by silicification of crocidolite (blue amphibole). The preserved fiber alignment behaves like thousands of tiny reflectors.
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Why it captivates
A crisp, traveling “eye” across golden bands; a classic optical effect appreciated across many jewelry styles.
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Care snapshot
Quartz toughness at Mohs 7; avoid harsh chemicals & prolonged heat (especially dyed/heat‑red stones). Clean with mild soap + water; soft cloth.

Identity & Naming 🔎

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.

Note on safety: Although the precursor mineral is asbestos, finished tiger’s eye is silica‑replaced. Normal wear is considered safe; lapidary work should control silica dust.

How It Forms 🧭

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).

Imagine a silk ribbon fossilized in quartz—tip it, and the ribbon flashes alive.

Palette & Pattern Vocabulary 🎨

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.

Physical & Optical Details 🧪

Property Typical Range / Note
Chemistry SiO₂ (quartz) replacing crocidolite; golden color from iron oxides/hydroxides.
Crystal system / Group Trigonal • Quartz (micro‑/crypto‑crystalline aggregate)
Hardness (Mohs) 7
Specific gravity ~2.64–2.71 (varies with iron content)
Refractive index / Optics ~1.544–1.553; birefringence ~0.009; aggregates may read ~1.54 spot.
Pleochroism None (color effects are reflective)
Luster / Transparency Silky to vitreous; opaque to translucent edges
Cleavage / Fracture No cleavage; conchoidal fracture
Phenomenon Chatoyancy (moving “eye”) from aligned micro‑fibers
Fluorescence Usually inert
Treatments Heat to produce red “bull’s eye”; dyeing for unusual hues (greens, vivid blues). Treatment status should be recorded in curatorial notes.
Field ID summary: golden moving band across straight stripes; quartz heft (SG ~2.65), spot RI ~1.54, no cleavage. Fiber‑optic glass imitators show a uniform eye and glassy bubbles/flow lines at 10×.

Under the Loupe 🔬

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.

Look‑Alikes & Imitations 🕵️

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.

Localities & Uses 📍

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.

Classification line example: “Tiger’s Eye — chatoyant quartz (SiO₂) — golden‑brown with moving band — treatment (none/heat/dyed) — locality.”

Care, Jewelry & Lapidary 🧼💎

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.
Observation tip: Place a golden cab beside a blue hawk’s eye and a red bull’s eye to illustrate the progression from precursor to treated/oxidized variants.

Hands‑On Demos 🔍

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.

Golden stripes, moving light—tiger’s eye shows how microstructure shapes optical behavior.

Questions ❓

Is tiger’s eye asbestos?
Its precursor is an asbestos mineral, but finished stones are quartz‑replaced. Normal wear is considered safe; lapidaries should manage silica dust.

Is red tiger’s eye natural?
Sometimes, but many red/burgundy stones are heat‑treated. Treatment status should be disclosed in records.

Why does the band look fuzzy?
Wavy or mixed fiber directions soften the eye, producing a broader silky sheen.

How to distinguish from imitations?
Fiber‑optic glass shows a uniform eye and glassy bubbles/flow lines at 10×. Natural tiger’s eye has banded, uneven stripes and quartz diagnostics.

Metaphysical note
Often referenced for themes of grounding, attention, and focus. (Cultural/subjective use; not a substitute for professional care.)

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