Phyllite

Main Elements:

Si, Al, K, Fe, Mg, O

Chemical Composition:

Similar to slate: fine-grained mica, quartz, and clay minerals, more recrystallized than slate

Density:

2.6-2.9 g/cm³

Compressive Strength:

Variable

Melting Point:

Variable

Formation:

Forms when shale is subjected to medium-grade metamorphism, more intense than slate but less than schist. The mica begins to recrystallize, creating a silky sheen.

Composition:

Composed of fine-grained mica, quartz, and clay minerals that have been partially recrystallized, giving it a silky appearance.

Types:

• Mica Phyllite
• Chlorite Phyllite

Etymology:

Derived from the Greek word "phyllon" meaning "leaf", referring to its foliated, leaf-like texture.

Uses:

• Decorative stone
• Roofing material
• Garden landscaping

Distribution:

Found worldwide in medium-grade metamorphic terrains

Historical Use:

Used as decorative stone and roofing material. Less common than slate or schist.

Symbolism:

Represents transition, transformation, and intermediate stages

What is the difference between phyllite, slate, and schist?

Slate is the lowest grade (fine-grained, no sheen), phyllite is intermediate (silky sheen), and schist is highest grade (coarse-grained, very shiny).

Why does phyllite have a silky sheen?

Phyllite's silky sheen comes from fine-grained mica minerals that have begun to recrystallize, reflecting light in a characteristic way.