How to identify Iron Ore with Malachite and Jarosite

To correctly identify Iron Ore with Malachite and Jarosite (Iron oxide (e.g., Goethite, Hematite) with Cu2(CO3)(OH)2 and KFe3(SO4)2(OH)6), check each of these features in order. Many rocks and minerals look alike, so cross-reference multiple properties before deciding.

Step-by-step identification

1. 1

   Color

   Overall color and any zoning or banding

   Iron oxides will be reddish-brown (Hematite) to yellowish-brown (Goethite). Malachite will be bright green to dark green. Jarosite will be yellow, yellowish-brown, or ochre-yellow.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Iron oxides can range from dull earthy to submetallic (Hematite). Malachite is typically silky, dull, or earthy. Jarosite is dull to vitreous.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Can be massive, botryoidal, reniform, or earthy for iron oxides and malachite. Jarosite often forms powdery coatings, crusts, or fine-grained masses.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Iron oxides are often massive, botryoidal, or stalactitic. Malachite can be botryoidal, stalactitic, fibrous, or massive. Jarosite typically forms minute tabular or pseudo-cubic crystals, often as crusts or earthy aggregates.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   Iron oxides (Goethite) have one perfect cleavage, but often not observed in massive forms. Hematite has no cleavage. Malachite has one perfect cleavage, but rarely seen. Jarosite has one perfect basal cleavage.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Oxidized zones of sulfide ore deposits, particularly those rich in iron and copper. Often found in gossans, which are weathered caps over sulfide bodies.

Key Facts

Hardness

Goethite: 5-5.5; Hematite: 5-6.5; Malachite: 3.5-4; Jarosite: 2.5-3.5 (Mohs scale).

Specific Gravity

Goethite: 3.3-4.3; Hematite: 5.26; Malachite: 3.9-4.03; Jarosite: 3.15-3.26.

Crystal System

Goethite: Orthorhombic; Hematite: Trigonal; Malachite: Monoclinic; Jarosite: Trigonal.

Color

Reddish-brown, yellowish-brown, bright green, yellow, ochre.

Luster

Earthy, dull, submetallic, silky, vitreous.

Transparency

Opaque (iron oxides, malachite, jarosite in bulk), translucent (thin malachite crystals).

Fracture

Conchoidal to uneven (iron oxides, malachite), splintery (jarosite).

Cleavage

Goethite: One perfect; Hematite: None; Malachite: One perfect; Jarosite: One perfect basal.

Composition

Iron oxides (FeO(OH), Fe2O3), copper carbonate hydroxide (Cu2(CO3)(OH)2), potassium iron sulfate hydroxide (KFe3(SO4)2(OH)6).

Physical characteristics

• Crystal Habit: Massive, botryoidal, reniform, stalactitic, fibrous, earthy, powdery, crusts, minute tabular crystals.
• Cleavage Type: Perfect in Goethite, Malachite, and Jarosite; absent in Hematite.
• Fracture Type: Conchoidal, uneven, splintery.
• Tenacity: Brittle.
• Luster Type: Earthy, dull, submetallic, silky, vitreous.

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