Slate

Main Elements:

Si, Al, K, Fe, O

Chemical Composition:

Similar to shale: clay minerals, quartz, and mica recrystallized under pressure

Density:

2.6-2.9 g/cm³

Compressive Strength:

100-200 MPa

Melting Point:

Variable

Formation:

Forms when shale is subjected to low-grade metamorphism (heat and pressure), causing the clay minerals to recrystallize and align into parallel layers.

Composition:

Composed of fine-grained mica, quartz, and clay minerals that have been recrystallized under pressure.

Types:

• Roofing Slate
• Writing Slate
• Flagstone Slate

Etymology:

Derived from the Old French word "esclate" meaning "splinter" or "fragment", referring to its tendency to split into thin sheets.

Uses:

• Roofing
• Flooring
• Writing surfaces (blackboards)
• Billiard tables
• Decorative stone

Distribution:

Found worldwide, especially in Wales, Spain, Brazil, and the eastern United States

Historical Use:

Used for roofing and writing surfaces for centuries. School blackboards were originally made of slate!

Symbolism:

Represents education, protection, and transformation

Why does slate split into thin sheets?

Slate splits into thin sheets because the minerals have been recrystallized and aligned into parallel layers under pressure, creating planes of weakness.

What is slate used for?

Slate is used for roofing, flooring, writing surfaces (blackboards), billiard tables, and decorative stone due to its ability to split into thin, flat sheets.