How to identify Iron-stained Quartzite

To correctly identify Iron-stained Quartzite (Quartzite with iron oxide staining), 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

   Typically ranges from pale yellow, orange, reddish-brown, to deep red and purplish-brown due to iron oxide staining. White, gray, or pinkish hues may be present where staining is less intense or absent.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to greasy on freshly broken surfaces, dull on weathered surfaces.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granoblastic, interlocking quartz grains. Fine-grained to medium-grained, rarely coarse-grained. Non-foliated, though relict bedding may be present.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Anhedral, interlocking quartz grains. Individual crystals are typically not well-formed.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   None, as quartz itself lacks cleavage. The rock breaks by fracturing across grain boundaries.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Forms in regional or contact metamorphic settings from quartz-rich sandstones. Often found in ancient mountain belts, cratonic shields, and areas that have undergone significant tectonic activity and burial. The iron staining can be primary (from iron in the original sediment) or secondary (from later fluid infiltration).

Key Facts

Hardness

7 (Mohs scale)

Specific Gravity

2.65 - 2.68 g/cm³

Crystal System

Trigonal (for quartz component)

Color

Variable, commonly reddish-brown, orange, yellow, or purplish due to iron oxide staining; also white, gray, pink.

Luster

Vitreous to greasy.

Transparency

Opaque to translucent.

Fracture

Conchoidal to subconchoidal, splintery.

Cleavage

None.

Composition

Primarily quartz (SiO2), typically >90%, with minor amounts of iron oxides (hematite, goethite, limonite), and possibly relict minerals from the original sandstone (e.g., feldspar, mica, zircon).

Physical characteristics

• Crystal Habit: Granular, interlocking anhedral grains.
• Cleavage Type: Absent.
• Fracture Type: Conchoidal to subconchoidal, splintery.
• Tenacity: Brittle.
• Luster Type: Vitreous to greasy.

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