How to identify Metasandstone

To correctly identify Metasandstone (Metasandstone), 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 light-colored, ranging from white, gray, and tan to reddish-brown, depending on the purity of the quartz and the presence of minor accessory minerals or iron oxides.

2. 2

   Luster

   How the surface reflects light: metallic, vitreous, dull

   Vitreous (glassy) to dull, depending on the grain size and degree of recrystallization.

3. 3

   Texture

   Grain size and surface feel: coarse, fine, glassy

   Granoblastic, with interlocking, equidimensional grains. Original clastic texture may be partially preserved or completely obliterated. Can be fine-grained to coarse-grained. May feel gritty if grains are not fully intergrown.

4. 4

   Crystal Form

   Shape of visible crystals or crystal faces

   Individual quartz grains are anhedral (lacking well-formed crystal faces) due to recrystallization and intergrowth.

5. 5

   Cleavage

   How it breaks: flat cleavage planes vs irregular fracture

   No true cleavage; fractures conchoidally or irregularly across grain boundaries. Unlike sandstone, it typically breaks through the quartz grains rather than around them.

6. 6

   Geological Environment

   The rock formation and setting where it occurs

   Formed in regional metamorphic settings (e.g., orogenic belts, continental collision zones) or contact metamorphic aureoles where sandstones are subjected to elevated temperatures and pressures. Often found in association with other metamorphic rocks like schists, gneisses, and slates.

Key Facts

Hardness

7 (Mohs scale, due to quartz content)

Specific Gravity

2.65 - 2.70 g/cm³

Crystal System

Trigonal (for quartz, the dominant mineral)

Color

White, gray, tan, reddish-brown, sometimes green or purple due to impurities.

Luster

Vitreous to dull

Transparency

Opaque to translucent (in thin sections or very fine-grained varieties)

Fracture

Conchoidal to irregular, often breaking across grains.

Cleavage

None (for the rock as a whole; quartz has poor to indistinct cleavage)

Composition

Predominantly quartz (SiO₂), typically >90%. Minor amounts of feldspar, mica (muscovite, biotite), chlorite, iron oxides, and other accessory minerals may be present.

Physical characteristics

• Crystal Habit: Granoblastic, interlocking anhedral grains of quartz.
• Cleavage Type: Absent in the rock; quartz has poor to indistinct cleavage.
• Fracture Type: Conchoidal to irregular.
• Tenacity: Brittle, very tough.
• Luster Type: Vitreous to dull.

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