Tiger Iron

SiO2 and Fe2O3 · Mohs 6.5 · N/A · Root Chakra

The stone of tiger iron: meaning, mineralogy, and somatic practice.

Energy & PassionProtection & GroundingMotivation & EnergyPatience & Endurance

This page documents traditional and cultural uses of tiger iron alongside emerging research on tactile grounding objects. Crystalis does not claim that tiger iron treats, cures, or prevents any medical condition. For mental health concerns, consult a qualified professional.

Crystalis Editorial · 40+ Years · Herndon, VA · 12 peer-reviewed sources

Origins: Australia (Western Australia), South Africa

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Materia Medica

Tiger Iron

The Triple Strength

Energy & PassionProtection & GroundingMotivation & Energy

Crystalis

Protocol

The Three-Band Endurance

Tiger eye, red jasper, and hematite banded together in a single stone — three minerals that individually represent vision, endurance, and grounding compressed into one aggregate that refuses to let you collapse in only one direction.

5 min

1
Hold the tiger iron and find all three bands: the golden-brown chatoyant bands of tiger eye, the red-brown of jasper, and the metallic silver-black of hematite. Each mineral formed under different conditions but geological pressure fused them into one stone. Press it against the center of your chest with your dominant hand.
2
Breathe into the hematite layer first — the heaviest component, specific gravity pushing the composite above 3.5. Iron oxide grounds. Inhale for four through your nose, exhale for six through your mouth. Feel your feet press into the ground. Your blood contains the same iron as those metallic bands. Five breaths for the iron.
3
Now breathe into the jasper layer — the endurance mineral. Microcrystalline quartz stained red with iron, formed slowly in sedimentary environments. Nothing dramatic created jasper. Just patience. Move the stone to your lower belly and breathe for thirty seconds without counting. Let rhythm find itself.
4
Finally, breathe into the tiger eye layer — vision. The chatoyant fibers are pseudomorphs of crocidolite replaced by quartz, preserving the shape of something that no longer exists. Your past selves are still visible in your current form. Move the stone to your forehead. Five breaths for seeing clearly.

Continue in the full protocol below.

tap to flip for protocol

The psyche gets tired of simplistic virtues. Be grounded. Be brave. Be focused. Be strong. Real life keeps demanding all of it at once, and the strain of being told to solve a composite problem with a single trait starts showing everywhere.

Tiger iron is convincing because it never tries. It layers reflective movement, metallic gravity, and earthy endurance without flattening any of them into the others. The result feels assembled for hard use.

Tiger iron matters when resilience has to become more intelligently mixed.

A layered defense is not confusion. It is design.

What Your Body Knows

Nervous system states

Tiger iron speaks most directly to states that require stamina rather than softness. Its structure is visibly layered, and that makes it useful as an object for bodies that feel split between action, fatigue, and guardedness.

One common state is stop-start exertion. The person can mobilize, but only in bursts. There is effort, then drag, then another brief surge. Tiger iron mirrors that rhythm without shaming it. Hematite-heavy bands suggest weight and stability. Jasper zones imply stored heat. Tiger eye contributes directional movement through chatoyant lines that appear to travel as light shifts. The stone presents endurance as a composite function, not a single mood.

Another state is defended productivity. The body is working hard, but underneath the output sits wariness. Shoulders stay high. Jaw stays set. Attention remains fixed on performance and protection at once. Tiger iron fits here because it is not purely reflective or purely dense. It carries metallic opacity beside brighter bands, which makes it apt for people doing difficult things while staying armored.

It also serves those in recovery from depletion who are not ready for gentle imagery. They need reminders of load-bearing strength with visible structure. A banded object can help because it suggests sequencing. Not everything has to happen simultaneously. One layer, then the next.

Tiger iron lands most precisely in the territory of sustained effort under pressure. It is less about emotional release and more about organizing force into durable strata.

dorsal vagal

- Depletion / collapse / burnout: Tiger Iron's geological story is one of endurance

When to use: - During periods of sustained effort requiring endurance - When the nervous system needs both grounding (hematite/jasper) and activation (tiger's eye) simultaneously - For practices involving bilateral awareness (the banding creates visual alternation)

Nervous system mapping based on polyvagal theory (Porges, S.W. The Polyvagal Theory. Norton, 2011).

The Earth Made This

Formation: How Tiger Iron Becomes Tiger Iron

Tiger iron is a banded metamorphic rock composed of alternating layers of tiger eye (silicified crocidolite), red jasper (iron-stained microcrystalline quartz), and hematite (iron oxide). It originates from banded iron formations (BIFs), Precambrian sedimentary deposits laid down 2. 2 to 2.

7 billion years ago when Earth's atmosphere was transitioning from anoxic to oxygenated conditions. The original sediment consisted of alternating layers of iron-rich and silica-rich material precipitated in shallow marine environments. Cyanobacterial oxygen production periodically oxidized dissolved iron, precipitating iron oxide layers between silica-rich layers.

Subsequent metamorphism and hydrothermal alteration transformed the silica layers into jasper and chalcedony, while some layers were infiltrated by crocidolite (blue asbestiform amphibole) that was later replaced by quartz . creating the chatoyant tiger eye component. The hematite layers retained their iron oxide composition.

The primary source is the Hamersley Basin in Western Australia, part of one of the world's largest BIF deposits. The interplay of metallic hematite, golden chatoyant tiger eye, and deep red jasper creates a visually distinctive material. Mohs hardness ranges from 5 (hematite) to 7 (quartz components).

Material facts

What the stone is made of

Mineralogy: Banded iron formation (BIF), not a single mineral. Composed of alternating bands of tiger eye (pseudomorphous quartz after crocidolite), red jasper (iron-rich microcrystalline quartz), and hematite (Fe₂O₃) or magnetite (Fe₃O₄). Crystal system: mixed. Mohs hardness: ~6.5 (variable by band). Specific gravity: 3.2-4.0 (higher than typical quartz, from hematite content). Color: golden-brown (tiger eye bands), red (jasper bands), silver-black (hematite bands). Luster: silky (tiger eye zones) to vitreous (jasper) to metallic (hematite). Habit: massive, banded. The banding reflects rhythmic sedimentation of silica and iron in Precambrian marine environments. Not a mineral species; a metamorphosed sedimentary rock.

Deeper geology

Across some of Earth's oldest sedimentary basins, tiger iron records a sequence that began more than two billion years ago in Precambrian seas. Long before animals colonized land, dissolved iron moved through ancient ocean water while silica precipitated in alternating pulses. Cyanobacterial oxygen production changed that chemistry. During intervals when oxygen rose, dissolved iron oxidized and settled out as hematite or magnetite. During quieter intervals, silica-rich layers accumulated instead. Those rhythmic deposits created banded iron formations, the ancestors of tiger iron.

The rock seen today is not a simple sediment left untouched. Burial, deformation, and hydrothermal alteration changed the original bands into a composite material with three visually distinct components. Jasper developed from iron-stained microcrystalline quartz, preserving the red layers. Metallic hematite retained the dense, reflective iron-rich bands. In some zones, blue crocidolite asbestos was later replaced by quartz while preserving its fibrous architecture. That pseudomorphic replacement produced tiger eye, the chatoyant golden-brown component whose silky flash moves as the stone is turned.

Tiger iron therefore combines sedimentary origin, metamorphic overprint, and replacement textures in one specimen. It is not a single mineral species but a rock assembled from several mineralogical events. Its hardness varies from band to band because quartz-rich zones resist abrasion differently from hematite-rich ones. Its density also feels unusual in the hand because iron oxides raise the specific gravity above that of ordinary jasper or chalcedony.

Western Australia's Hamersley Basin is the classic source because it hosts immense Archean to Paleoproterozoic iron formations altered on a grand scale. The visual drama comes from that deep history: metallic black, blood red, and golden chatoyancy aligned in stripes. Each band is a separate chapter. Sedimentation laid down the rhythm. Metamorphism compacted it. Silica replacement introduced luster and movement. What emerges is a composite stone in which ancient seawater chemistry, iron oxidation, and later mineral substitution remain visible all at once. That composite origin is why polished pieces can look like three stones fused into one narrative. Few lapidary materials preserve ancient seawater chemistry, iron oxidation, and pseudomorphic replacement so legibly in a single banded slab. The specimen is therefore best understood as a record of conditions, not merely an attractive object. Its structure, habit, and chemistry all preserve the environment that made it possible.

Mineralogy

Mineral specs

Chemical Formula

SiO2 and Fe2O3

Crystal System

N/A

Mohs Hardness

6.5

Specific Gravity

3.2-4.0 (higher than typical quartz due to hematite content)

Luster

Vitreous to silky (tiger's eye bands show characteristic chatoyancy); metallic to submetallic (hematite bands)

Color

Red-Yellow-Black

Traditional Knowledge

Lore and culture around Tiger Iron

Science grounds the page. Tradition, lore, and remembered use make it readable as lived knowledge.

Timeline: ~2.5-3.5 billion years ago: Formation during Archean-Paleoproterozoic Geological significance recognized in 19th-20th century as key evidence for early Earth atmospheric evolution Late 20th century: Gained popularity as lapidary and metaphysical material 2000s-present: BIFs central to understanding the Great Oxidation Event and early life

Trade name origin: "Tiger Iron" combines "tiger's eye" (for the chatoyant bands) with "iron" (for the dominant hematite component). The name is a lapidary/trade designation, not a geological term. Geologists refer to it as "tiger's eye-bearing banded iron formation."

Geological significance: Tiger Iron is literally a fragment of early Earth's ocean chemistry, recording the transition from an anoxic to an oxygenated world. Each band preserves evidence of microbial processes that fundamentally transformed the planet's atmosphere.

Unknown

Timeline

- ~2.5-3.5 billion years ago: Formation during Archean-Paleoproterozoic - Geological significance recognized in 19th-20th century as key evidence for early Earth atmospheric evolution - Late 20th century: Gained popularity as lapidary and metaphysical material - 2000s-present: BIFs central to understanding the Great Oxidation Event and early life

Unknown

Trade name origin

"Tiger Iron" combines "tiger's eye" (for the chatoyant bands) with "iron" (for the dominant hematite component). The name is a lapidary/trade designation, not a geological term. Geologists refer to it as "tiger's eye-bearing banded iron formation."

Unknown

Geological significance

Tiger Iron is literally a fragment of early Earth's ocean chemistry, recording the transition from an anoxic to an oxygenated world. Each band preserves evidence of microbial processes that fundamentally transformed the planet's atmosphere.

Sacred Match Notes

When this stone becomes the right door

Sacred Match prescribes Tiger Iron when you report:

Running in bursts then crashing

Muscular tension from constant effort

Guarded productivity

Trouble sustaining momentum

Feeling split between grit and exhaustion

Needing stronger physical resolve

Sacred Match prescribes through physiological diagnosis, not preference. It queries the nervous system: current sensation, protective mechanism, and the biological need masked by both. When that triangulation reveals stop-start drive, defended action, or depleted stamina that still has work to do, tiger iron enters the protocol.

Bursting -> energy spent unevenly -> seeking endurance

Tense -> effort fused with defense -> seeking grounded output

Guarded -> productivity under armor -> seeking safer strength

Crashing -> reserves not lasting -> seeking layered support

Split -> heat and heaviness together -> seeking integration It is prescribed for bodies that still have force available but need that force layered, paced, and protected so it does not burn out in a single push. The prescription stays narrow on purpose, matching material logic to body state rather than treating every bright stone as interchangeable.

3-Minute Reset

The Three-Band Endurance

5 min protocol

1
Hold the tiger iron and find all three bands: the golden-brown chatoyant bands of tiger eye, the red-brown of jasper, and the metallic silver-black of hematite. Each mineral formed under different conditions but geological pressure fused them into one stone. Press it against the center of your chest with your dominant hand.
1 min
2
Breathe into the hematite layer first — the heaviest component, specific gravity pushing the composite above 3.5. Iron oxide grounds. Inhale for four through your nose, exhale for six through your mouth. Feel your feet press into the ground. Your blood contains the same iron as those metallic bands. Five breaths for the iron.
1 min
3
Now breathe into the jasper layer — the endurance mineral. Microcrystalline quartz stained red with iron, formed slowly in sedimentary environments. Nothing dramatic created jasper. Just patience. Move the stone to your lower belly and breathe for thirty seconds without counting. Let rhythm find itself.
1 min
4
Finally, breathe into the tiger eye layer — vision. The chatoyant fibers are pseudomorphs of crocidolite replaced by quartz, preserving the shape of something that no longer exists. Your past selves are still visible in your current form. Move the stone to your forehead. Five breaths for seeing clearly.
1 min
5
Return the stone to your chest. All three layers, all three functions — grounding, endurance, vision — held in one composite. You do not need three separate stones. You do not need three separate practices. Place the tiger iron down. You are already the composite. Walk out as all three.
1 min

The #1 Question

Can Tiger Iron go in water?

Safe for brief water contact; stable mineral assemblage

Mineral Distinction

What sets Tiger Iron apart

Dealers routinely sell tiger iron as if it were just a darker tiger eye, but that shortcut hides the most important fact: tiger iron is a layered rock, not a single chatoyant quartz material.

Tiger eye contains silicified crocidolite with a golden sheen and usually lacks the thick red jasper and metallic hematite bands that define tiger iron. Banded iron formation is even broader. It refers to the ancient iron-silica rock unit itself, often without enough tiger eye replacement to create strong chatoyancy. Tiger iron sits between them: a decorative lapidary material built from tiger eye, jasper, and hematite in obvious parallel bands.

The fastest check is visual and tactile together. If the stone shows gold shimmer, brick-red zones, and silver-black metallic layers in one polished piece, it is likely tiger iron. Plain tiger eye will be lighter, more uniform, and far less metallic. Generic jasper may carry red and brown tones but will not flash.

The price gap is real, but so is the geology. Calling every striped brown cabochon tiger iron flattens a very specific story about Precambrian oceans, iron deposition, and later quartz replacement.

Care and Maintenance

How to care for Tiger Iron

- Asbestos note: The tiger's eye component originally formed from crocidolite (blue asbestos). In finished/polished tiger iron, the crocidolite has been completely replaced by quartz (pseudomorphic replacement). Polished specimens pose no asbestos risk.

However, rough/unprocessed material from some localities may contain residual unsilicified crocidolite fibers. Do NOT cut, grind, or sand raw tiger iron without proper respiratory protection and wet-cutting methods (Gaffney et al. , 2016; Mandel et al.

, 2016; Holton et al. , 2022). - Water safety: Safe for brief water contact; stable mineral assemblage - Sun safety: Generally stable; prolonged intense UV may fade tiger's eye bands over extended periods - Iron content: Wash hands after extended handling; iron oxide can stain skin and clothing

Crystal companions

What pairs well with Tiger Iron

Hematite **The Iron on Iron.** Tiger iron already contains hematite as one of its banded components, but pairing it with a distinct hematite piece intensifies the dense, anchoring quality without obscuring the stone's layered complexity. Tiger iron is SiO2 and Fe2O3 banded together at Mohs 6.5, shimmer and weight in alternating stripes. Suited to periods of scattered effort when endurance matters more than speed. Keep tiger iron in a trouser pocket and place hematite at the feet during a seated practice.

Carnelian **The Action With Stamina.** The red jasper bands in tiger iron suggest stored heat, while carnelian contributes cleaner forward motion from its own iron-oxide warmth. Best when motivation exists but keeps stalling halfway through the day. Place tiger iron near the lower abdomen and carnelian on the desk beside active work.

Black Tourmaline **The Composite Shield.** Tiger iron offers multiple textures in one stone: chatoyant shimmer, metallic mass, and red earth. Black tourmaline adds a simpler, harder boundary at Mohs 7 with piezoelectric charge. Designed for when a room feels chaotic and the body needs both resilience and a perimeter. Set tiger iron in the corner of a workspace and keep black tourmaline by the entry.

Clear Quartz **The Pattern Recognition.** Tiger iron's bands are easiest to read when paired with a stone that amplifies observation rather than density. Clear quartz helps turn the layered look into a layered reflection on habits, timelines, and repeating effort. Hold quartz at eye level and rest tiger iron in the lap during journaling.

In Practice

How Tiger Iron is used

Nervous system states addressed: - Depletion / collapse / burnout: Tiger Iron's geological story is one of endurance. 2.5+ billion years of surviving metamorphism, tectonic upheaval, and erosion. The density (heavier than typical stones of similar size) provides strong grounding input. The tripartite composition (hematite/jasper/tiger's eye) offers three distinct textures and visual frequencies in one stone. - Freeze / immobility: The chatoyant flash of the tiger's eye bands catches the eye and can serve as an orienting stimulus, pulling attention outward from internal freeze states. - Low vitality / chronic fatigue: The iron-dominant composition and warm color palette (red, gold, silver) have been traditionally associated with vitality and stamina in somatic crystal practice.

When NOT to use: - During acute hyperarousal where stimulating stones may escalate activation - When the person needs softness and receptivity rather than strength and endurance - When anxiety is present. the metallic flash of tiger's eye can be overstimulating for some nervous systems

Verification

Authenticity

Tiger iron: banded rock with three components: tiger eye (chatoyant, silky), red jasper (opaque, red), and hematite (metallic, dark). SG 3. 2-4.

0 (heavier than pure quartz due to hematite). All three layers should be naturally intergrown. If the banding looks painted or if any layer is absent, it is a different banded rock.

The chatoyancy should be visible in the tiger eye bands when rotated under light.

Temperature

Natural Tiger Iron should usually feel cooler than plastic or resin on first touch and warm more slowly in the hand.

Scratch logic

Use 6.5 on the Mohs scale as the check, not internet myths. A real specimen should behave in line with the hardness listed above.

Surface and luster

Look for a vitreous to silky (tiger's eye bands show characteristic chatoyancy); metallic to submetallic (hematite bands) surface quality rather than a painted or plastic shine.

Weight and density

The listed specific gravity is 3.2-4.0 (higher than typical quartz due to hematite content). If a specimen feels unusually light for its size, it may deserve a second look.

Geographic Origins

Where Tiger Iron forms in the world

Ord Ranges and Hamersley Basin, Western Australia (primary commercial source; Pilbara Craton BIFs ~2.5 Ga) Griquatown, Northern Cape Province, South Africa (Transvaal Supergroup BIFs ~2.4 Ga) Marra Mamba Formation, Western Australia

Tiger Iron is a variety of banded iron formation (BIF) that formed during the Archean-Paleoproterozoic eons (approximately 2.5-3.5 billion years ago), making it among the oldest rocks used in lapidary work. BIFs represent one of the most significant rock types in Earth's geological record, forming during a unique period when the oceans contained abundant dissolved ferrous iron (Fe2+) and atmospheric oxygen was minimal. The alternating bands of iron-rich and silica-rich layers record episodic precipitation driven by changes in ocean chemistry, microbial activity, and oxygen production. Research on Archean BIF from the Yellowknife greenstone belt demonstrates that the characteristic mesobanding (cm-scale Fe-rich and Si-rich alternation) predates peak metamorphism, confirming a primary depositional origin subsequently modified by metamorphic recrystallization (Katsuta et al., 2012). The deposition of BIF involved complex biogeochemical cycling. Microbiological processes played central roles: anoxygenic photoferrotrophic bacteria oxidized dissolved Fe2+ to Fe3+ using light energy, while cyanobacteria contributed oxygen that abiotically oxidized additional iron. The resulting ferric iron precipitated as ferrihydrite, which subsequently transformed to hematite and other iron oxides during diagenesis and metamorphism. Silica precipitation occurred from seawater supersaturated with dissolved silica (no silica-secreting organisms existed in the Archean). The rhythmic alternation may reflect seasonal, tidal, or longer-period environmental cycles (Posth et al., 2013; Nims & Johnson, 2022; Ward et al., 2017).

FAQ

Frequently asked

What is Tiger Iron?

Tiger Iron is classified as a Metamorphosed sedimentary rock (banded iron formation) -- NOT a single mineral. Chemical formula: Composite:. Mohs hardness: 6.5-7 (dominated by quartz/jasper hardness). Crystal system: Not applicable (polycrystalline aggregate).

What is the Mohs hardness of Tiger Iron?

Tiger Iron has a Mohs hardness of 6.5-7 (dominated by quartz/jasper hardness).

Can Tiger Iron go in water?

Safe for brief water contact; stable mineral assemblage

Can Tiger Iron go in the sun?

Generally stable; prolonged intense UV may fade tiger's eye bands over extended periods

What crystal system is Tiger Iron?

Tiger Iron crystallizes in the Not applicable (polycrystalline aggregate).

What is the chemical formula of Tiger Iron?

The chemical formula of Tiger Iron is Composite:.

Where is Tiger Iron found?

- Ord Ranges and Hamersley Basin, Western Australia (primary commercial source; Pilbara Craton BIFs ~2.5 Ga) - Griquatown, Northern Cape Province, South Africa (Transvaal Supergroup BIFs ~2.4 Ga) - Marra Mamba Formation, Western Australia

How does Tiger Iron form?

References

Sources and citations

Gaffney, Shannon H., Grespin, Matthew, Garnick, Lindsey, Drechsel, Derek A., Hazan, Rebecca et al. (2016). Anthophyllite asbestos: state of the science review. Journal of Applied Toxicology. [SCI]
DOI: 10.1002/jat.3356
Poulet, Thomas, Giraldo, Juan Felipe, Ramanaidou, Erick, Piechocka, Agnieszka, Calo, Victor M. (2022). Paleo‐stratigraphic permeability anisotropy controls supergene mimetic martite goethite deposits. Basin Research. [SCI]
DOI: 10.1111/bre.12723
Yang, Xiuqing, Mao, Jingwen, Li, Rongxi, Jiang, Zongsheng, Yu, Miao et al. (2022). The deposition and significance of an Ediacaran non‐glacial iron formation. Geobiology. [SCI]
DOI: 10.1111/gbi.12518
Mandel, Jeffrey H., Alexander, Bruce H., Ramachandran, Gurumurthy. (2016). A review of mortality associated with elongate mineral particle (EMP) exposure in occupational epidemiology studies of gold, talc, and taconite mining. American Journal of Industrial Medicine. [SCI]
DOI: 10.1002/ajim.22641
Upadhyay, Rajendra Kumar, Venkatesh, Akella Satya, Roy, Subrata. (2010). Mineralogical Characteristics of Iron Ores in Joda and Khondbond Areas in Eastern India with Implications on Beneficiation. Resource Geology. [SCI]
DOI: 10.1111/j.1751-3928.2010.00126.x
Moriyama, Takeru, Panigrahi, Mruganka K., Pandit, Dinesh, Watanabe, Yasushi. (2008). Rare Earth Element Enrichment in Late Archean Manganese Deposits from the Iron Ore Group, East India. Resource Geology. [SCI]
DOI: 10.1111/j.1751-3928.2008.00072.x
Adomako‐Ansah, Kofi, Mizuta, Toshio, Hammond, Napoleon Q., Ishiyama, Daizo, Ogata, Takeyuki et al. (2013). Gold Mineralization in Banded Iron Formation in the <scp>A</scp>malia <scp>G</scp>reenstone <scp>B</scp>elt, <scp>S</scp>outh <scp>A</scp>frica: A Mineralogical and Sulfur Isotope Study. Resource Geology. [SCI]
DOI: 10.1111/rge.12000
Ganno, Sylvestre, Tsozué, Désiré, Kouankap Nono, Gus Djibril, Tchouatcha, Milan Stafford, Ngnotué, Timoléon et al. (2018). Geochemical Constraints on the Origin of Banded Iron Formation‐Hosted Iron Ore from the Archaean Ntem Complex (Congo Craton) in the Meyomessi Area, Southern Cameroon. Resource Geology. [SCI]
DOI: 10.1111/rge.12172
KATSUTA, N., SHIMIZU, I., HELMSTAEDT, H., TAKANO, M., KAWAKAMI, S. et al. (2012). Major element distribution in Archean banded iron formation (BIF): influence of metamorphic differentiation. Journal of Metamorphic Geology. [SCI]
DOI: 10.1111/j.1525-1314.2012.00975.x
Posth, Nicole R., Konhauser, Kurt O., Kappler, Andreas. (2013). Microbiological processes in banded iron formation deposition. Sedimentology. [SCI]
DOI: 10.1111/sed.12051
Ward, L. M., Idei, A., Terajima, S., Kakegawa, T., Fischer, W. W. et al. (2017). Microbial diversity and iron oxidation at Okuoku‐hachikurou Onsen, a Japanese hot spring analog of Precambrian iron formations. Geobiology. [SCI]
DOI: 10.1111/gbi.12266
Nims, Christine, Johnson, Jena E. (2022). Exploring the secondary mineral products generated by microbial iron respiration in Archean ocean simulations. Geobiology. [SCI]
DOI: 10.1111/gbi.12523

Closing Notes

Tiger Iron

Tiger eye, red jasper, and hematite in alternating bands. Three iron-bearing minerals layered in Archean banded iron formations, 2. 5 billion years old.

The science documents some of the oldest sedimentary iron deposits on Earth. The practice asks what strength means when three forms of the same element take turns holding the structure.

Field Notes