Quartzite Pebble

Hardness of 7 on Mohs scale, yellowish-tan to gray color due to iron staining, vitreous to dull luster, granular texture where individual sand grains are fused, lacks cleavage, high specific gravity (~2.6-2.7).

Formed through the metamorphism of quartz-rich sandstone. High heat and pressure in tectonic environments cause the original quartz grains to recrystallize into an interlocking mosaic of crystals. Over time, erosion rounds these rocks into river pebbles.

Commonly used as crushed stone in road construction, as railroad ballast, or as a source of silica in glass manufacturing. Smooth pebbles are often used in landscaping and decorative masonry.

Quartzite is so tough that it often survives intense mechanical weathering, which is why it is frequently found as rounded pebbles in stream beds long after softer rocks have eroded away. It is often mistake for quartz, but the granular texture distinguishes it.

Identify by its hardness (it will easily scratch glass) and the way it breaks through sand grains rather than around them. Common in glacial till and riverbeds worldwide. Look for a sugary, crystalline surface when freshly broken.