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Hematite is an iron oxide mineral with the chemical formula Fe2O3. It is the most abundant iron ore and is characterized by its distinctive reddish-brown streak, regardless of its external color. Its appearance can vary significantly, from metallic gray to dull red, and its crystal habits range from massive, botryoidal (kidney ore), micaceous (specular hematite), to oolitic. It is a common rock-forming mineral and a significant component of many sedimentary, metamorphic, and igneous rocks.
How to Identify
- Color
- Variable: steel-gray, silver-gray, black, reddish-brown, or red. The color can be metallic, dull, or earthy.
- Luster
- Metallic (specular hematite), submetallic, dull, or earthy.
- Texture
- Can be massive, granular, botryoidal (kidney ore), reniform, mammillary, micaceous (specular hematite), columnar, or oolitic.
- Crystal Form
- Typically forms in the trigonal system. Crystals are often tabular, rhombohedral, or platy. Massive, botryoidal, and micaceous forms are common.
- Cleavage
- None. Hematite exhibits no true cleavage, but it can show a parting parallel to the basal pinacoid {0001} and rhombohedral faces {1011}.
- Geological Environment
- Found in igneous, metamorphic, and sedimentary rocks. Common in Banded Iron Formations (BIFs), hydrothermal veins, contact metamorphic deposits, and as an alteration product in weathered rocks and soils.
Key Facts
- Hardness: 5.5-6.5 on the Mohs scale
- Specific Gravity: 4.9-5.3
- Crystal System: Trigonal
- Color: Steel-gray, black, reddish-brown, or red
- Luster: Metallic, submetallic, dull, or earthy
- Transparency: Opaque
- Fracture: Uneven to subconchoidal
- Cleavage: None (parting sometimes observed)
- Composition: Iron oxide (Fe2O3)
Quick Check
- Color: Steel-gray, black, reddish-brown, or red
- Luster: Metallic, submetallic, dull, or earthy
- Streak: Reddish-brown to blood-red
Physical Characteristics
- Crystal Habit: Massive, botryoidal, reniform, mammillary, micaceous (specular hematite), columnar, tabular, rhombohedral, oolitic.
- Cleavage Type: None. Parting on {0001} and {1011} is sometimes observed due to twinning or exsolution lamellae.
- Fracture Type: Uneven to subconchoidal.
- Tenacity: Brittle.
- Luster Type: Metallic, submetallic, dull, or earthy.
Formation
Hematite forms in a wide variety of geological environments. It is a primary mineral in some igneous rocks, a common accessory mineral in metamorphic rocks, and a significant component of sedimentary rocks, especially Banded Iron Formations (BIFs). It can form through direct precipitation from iron-rich waters, oxidation of other iron minerals (like magnetite or pyrite), or hydrothermal processes. In BIFs, it is believed to have precipitated from ancient oceans rich in dissolved iron, often in conjunction with microbial activity.
Usage
Hematite is the most important ore of iron, accounting for over 90% of global iron production. It is used to produce steel, which is fundamental to construction, automotive, and manufacturing industries. Finely ground hematite is used as a red pigment (ochre) in paints, cosmetics, and polishing compounds. High-quality specimens are sometimes used as gemstones or ornamental stones. It also has minor uses in radiation shielding and as a heavy medium in coal preparation.
Age Distribution
Found in rocks of all ages, but particularly abundant in Precambrian Banded Iron Formations (BIFs) dating back 1.8 to 2.5 billion years.
Where to Find
Lake Superior Region, USA (Michigan, Minnesota, Wisconsin)
World-renowned for vast deposits of high-grade hematite in Banded Iron Formations (BIFs), particularly the Mesabi Range.
Minas Gerais, Brazil
Significant deposits of high-grade hematite, including large quantities of 'itabirite' (a banded iron formation rich in hematite).
Pilbara Region, Western Australia
One of the largest iron ore provinces globally, with extensive hematite deposits in BIFs.
Krivoy Rog, Ukraine
Major iron ore basin with substantial hematite reserves.
Cumbria, England
Historically famous for high-quality 'kidney ore' hematite specimens.
Finding Tips
Streak Test is Key
Always perform a streak test. Hematite's characteristic reddish-brown streak is its most reliable diagnostic property, distinguishing it from other dark, metallic minerals like magnetite or galena.
Look for Heavy Samples
Hematite has a relatively high specific gravity (4.9-5.3), so samples will feel noticeably heavy for their size compared to many other common minerals.
Observe Luster and Habit
Note the luster (metallic, dull, earthy) and crystal habit (massive, botryoidal, micaceous). Specular hematite (micaceous, metallic) and kidney ore (botryoidal, metallic to submetallic) are particularly distinctive forms.
Check for Magnetism (or lack thereof)
Unlike magnetite, hematite is generally non-magnetic. Weak magnetism can occur if it contains inclusions of magnetite or if it has been heated, but it is not inherently magnetic.
Similar Rocks
Magnetite
Magnetite
Also known as: Lodestone
Goethite
Goethite
Also known as: Bog Iron
Limonite
Limonite (a mixture of hydrated iron oxides, primarily goethite)
Also known as: Bog Iron, Brown Iron Ore
Pyrite
Pyrite
Also known as: Fool's Gold
Scientific Classification
- Mineral Class
- Oxides
- Group
- Corundum-Hematite Group
- Crystal System
- Trigonal
- Chemical Formula
- Fe2O3
- Composition
- Iron(III) oxide
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