Hematite: The Silver Mineral With a Blood-Red Streak

Short answer: hematite is iron oxide, Fe2O3, the most important ore of iron and one of the most common minerals at Earth's surface. It looks steel gray, black or silvery in a polished piece, yet always grinds to a red to reddish brown powder, which is the single best way to identify it. Collectors know it as glittering specularite, rounded kidney ore and rosette "iron roses"; it also stains countless other stones red.

What is hematite, mineral by mineral?

Strip away the shop names and hematite is a simple compound: two iron atoms to three oxygen atoms. Webmineral gives the composition as 69.94 % iron and 30.06 % oxygen by weight, puts it in the trigonal crystal system in the corundum-hematite group, and lists a density of 5.3. That group placement is worth a second look: hematite shares its structure type with corundum, the mineral that becomes ruby and sapphire, with iron sitting where aluminum would be.

The name points straight at the streak. Webmineral traces it to the Greek haimatites, "bloodlike", in allusion to vivid red color of the powder. The International Gem Society makes the same point and adds that most hematite is black or gray in hand, red only in thin slivers or crystals.

How do you identify hematite?

Three checks settle almost every case: streak, weight and luster.

The streak plate

Scrape a corner across unglazed porcelain. Geology.com's streak test guide explains that hematite specimens can be black, red, brown or silver, yet all of them leave a streak with a reddish color. A metallic piece needs a little care: per Geology.com's hematite article, brittle specimens leave a trail of glittering fragments along with the powder, so shake or lightly brush the loose debris away before reading the color underneath.

Weight in the hand

A polished hematite tumble feels heavy for its size. With a specific gravity around 5, it weighs about twice as much as a quartz pebble of the same volume, and that "weighty feel" is part of why tumbled hematite sells so well.

What else looks like it?

Several dark, metallic minerals can pass for hematite at a glance. Minerals.net notes that lepidocrocite also has a red streak but is softer, at 4.5 to 5, and that goethite is less lustrous. The IGS adds that hematite conducts electricity weakly, unlike the manganese oxide psilomelane, which it resembles. Magnetite is the other common confusion; it streaks black. The magnet question, and the man-made beads sold as "magnetic hematite", have their own guide: is magnetic hematite real?

How does hematite form?

Hematite turns up in igneous, metamorphic and sedimentary rocks, but the deposits that matter most are sedimentary. Geology.com describes how, from about 2.4 billion years ago, the first photosynthesizing cyanobacteria released free oxygen into oceans rich in dissolved iron; the oxygen combined with the iron to form hematite, which settled on the seafloor. The result is the banded iron formation: layers of hematite alternating with jasper, chert or shale. Mined rock from these formations is often called taconite.

The Geology.com iron ore page adds that nearly all of Earth's major iron ore deposits are in rocks that formed over 1.8 billion years ago. A polished slab of banded iron formation, with silver hematite stripes between red jasper bands, is a cross section through that early chemistry.

Hematite also grows in cavities from hydrothermal fluids, crystallizes from magma, and forms in contact metamorphism. Kidney ore is the cavity form: it grows unrestricted into open space, and Geology.com notes that this chemically precipitated hematite tends to be purer than the sedimentary kind, which made it the hematite of choice for pigments.

What are the main forms and trade names?

Hematite has more looks than most minerals. The names collectors use:

• Specularite (specular or micaceous hematite): intergrown hexagonal plates that glitter when the piece is turned. It looks like a rock made of silver mica flakes but still streaks red.
• Kidney ore: rounded, botryoidal or reniform masses. Cumbria in England is the classic source.
• Iron rose: flat hexagonal plates grouped into a rosette. Minerals.net lists the Thomas Range in Utah and Arizona localities including Bouse and the Buckskin Mountains.
• Martite: hematite that has replaced magnetite, keeping magnetite's octahedral shape.
• Oolitic hematite: tiny round spheres of precipitated hematite, a common iron ore texture.
• Rainbow or iridescent hematite: natural crystals with a play of color from thin surface films, notably from Minas Gerais, Brazil.
• Paint ore: soft, earthy red hematite.

Webmineral also records a striking intergrowth: golden needles of rutile grown epitaxially on black hematite crystals from Novo Horizonte, Bahia, Brazil, the "rutile star on hematite" pieces collectors chase.

Where does collector hematite come from?

Minerals.net names the standout localities. Large, thick crystals come from Minas Gerais, Brazil, at places such as Itabira and Congonhas; lustrous tabular plates come from Novo Horizonte and Brumado in Bahia. Rio Marina on the island of Elba, Italy, is a historic classic, and the Cavradi Gorge in Switzerland is known for lustrous tabular crystals. The Wessels Mine in South Africa's Kalahari manganese field has produced rare prismatic forms. Most tumbled, polished hematite on the market comes from Minas Gerais.

For iron, the scale is different. The USGS states that iron ore almost always consists of magnetite and hematite, that almost all of it (98 %) goes into steelmaking, and that Australia and Brazil each supply about one third of world exports. Minerals.net puts hematite at roughly 90 percent of all iron mined in the United States, with US production centered on Michigan and Minnesota.

Why is so much quartz red?

Hematite is a pigment before it is a gem. Geology.com notes that people were crushing it into paint at least 40,000 years ago, and Minerals.net points out that small amounts of hematite cause the color of most red and brown rock. Inside quartz, it shows as red clouds, flakes, phantoms and surface coatings: the color in many "red quartz", "fire quartz" and "hematoid quartz" pieces. In tiger's eye, iron oxides drive the golden-brown and red tones. When a listing calls quartz "hematite quartz", the hematite is usually an inclusion or coating, and the host is ordinary quartz; the inclusions guide explains how one mineral gets trapped in another.

Geology.com even takes the story off planet: NASA found hematite among the most abundant minerals in the rocks and soils of Mars, which is why the planet looks red. The Opportunity rover's 2004 "blueberries" turned out to be tiny spheres of mostly hematite.

How do you care for hematite?

Hardness of 5 to 6.5 means a hematite ring stone scuffs against harder grit and chips on impact; the IGS calls the material reasonably tough but brittle, and recommends protective settings for rings. Clean it with a soft brush, mild detergent and warm water, and skip steam and ultrasonic cleaners. Specularite flakes easily, so handle specimens by their matrix. Store polished hematite away from quartz pieces, which can scratch it.

What is hematite associated with in tradition?

In crystal traditions, hematite is associated with strength, steadiness and protection, an association the IGS links to its blood-red powder. Warriors in older lore were said to rub it on the skin for protection in battle.

What to look for when you buy hematite

Decide first whether you want hematite itself or hematite as a guest inside quartz. For hematite itself, polished tumbles are the cheapest way to own and test the real mineral; ask for the streak, feel the weight, and expect no strong pull from a magnet. For crystals, look for sharp plates, an intact rosette, and a named locality; Bahia, Minas Gerais, Elba and Cumbria are all signs of a dealer who tracks provenance. For hematite in quartz, look at whether the red is inside the crystal or only on the surface, since coatings can wear.

• Hematite tumbles: small polished pieces of the real mineral, ideal for running a streak test on the back of a tile and feeling hematite's weight.
• Hematite in Quartz Tumbles: polished quartz with rust-red iron oxide trapped inside, a cheap way to see hematite as an inclusion.
• Red Quartz (Hematite): raw quartz crystals stained and coated red; check the listing photos for how much of the color sits on the faces.
• Hematite Quartz: raw hematite-included quartz, useful next to the red quartz to compare an inclusion with a coating.
• Hematoid quartz sphere: a polished sphere where the hematite shows as red flecks and clouds; turn it under one light to see the inclusions at different depths.

Frequently asked questions

What color is hematite's streak?

Red to reddish brown, every time. A hematite specimen can be silver, black, gray, brown or red in hand, but its powder on unglazed porcelain is always reddish. That consistency is what makes the streak the most useful identification test for this mineral.

How hard is hematite?

Hematite sits at 5 to 6.5 on the Mohs scale, depending on the form. Massive and crystalline pieces are at the harder end, while specularite and earthy forms crumble or flake. It scratches glass with effort but can itself be scratched by quartz.

Is hematite heavy?

Yes. Its specific gravity is about 5.0 to 5.3, roughly twice that of quartz, so a hematite tumble feels noticeably dense compared with an agate or jasper pebble of the same size. That density is one of the quickest hand checks.

What is specular hematite?

Specular hematite, or specularite, is hematite made of small intergrown hexagonal plates that sparkle like mica when the specimen moves. Despite its silver flash, it still produces a red streak. Classic sources include Cumbria in England and the Thomas Range in Utah.

What is kidney ore?

Kidney ore is hematite that grew into open cavities as rounded, botryoidal masses resembling internal organs. Cumbria in England is the classic locality. Because it grew from solution in open space, it is often purer than layered sedimentary hematite.

Sources

• Webmineral, Hematite Mineral Data: https://webmineral.com/data/Hematite.shtml
• Geology.com, Hematite: https://geology.com/minerals/hematite.shtml
• Geology.com, The Streak Test for Minerals: https://geology.com/minerals/streak-test.shtml
• Geology.com, Iron Ore: https://geology.com/rocks/iron-ore.shtml
• Minerals.net, The mineral hematite: https://www.minerals.net/mineral/hematite.aspx
• International Gem Society, Hematite Value, Price, and Jewelry Information: https://www.gemsociety.org/article/hematite-jewelry-and-gemstone-information/
• U.S. Geological Survey, Iron Ore Statistics and Information: https://www.usgs.gov/centers/national-minerals-information-center/iron-ore-statistics-and-information