Slate with Pyrite Inclusions

Physical Properties

Black to dark gray color, fine-grained, foliated texture. Hardness 2.5-4 for slate, 6-6.5 for pyrite inclusions. Luster is dull for matrix with metallic brassy specks. Slaty cleavage.

Formation & Geological History

Formed by low-grade regional metamorphism of shale or mudstone under high pressure and low heat. Common in Paleozoic and Precambrian formations.

Uses & Applications

Used for roofing tiles, billiard tables, floor tiles, and garden landscaping. Pyrite crystals are sought after by hobbyist collectors.

Geological Facts

Slate can easily be split into thin, flat sheets. When pyrite crystals are present, they are often referred to as 'Fool's Gold' and can form perfect cubes or framboidal clusters within the rock layers.

Field Identification & Locations

Identify in the field by its ability to split along flat planes (slaty cleavage) and its 'clink' sound when struck. Common in mountainous regions like Wales, Pennsylvania, and the Himalayas.

Identified on: 5/19/2026

Mode: Standard