Lava Rock vs River Rock: Size, Cost, and Which to Use

Lava Rock

Lava rock is a lightweight, porous volcanic stone commonly used in landscaping. Its rough texture helps retain moisture while allowing airflow to plant roots.

River Rock

River rock is naturally rounded stone from river beds and glacial gravel deposits, washed and screened into size bands from 3/4 inch to 8 inches. It costs $40 to $100 per ton in 2026, weighs 1.35 to 1.6 tons per cubic yard, and is the go-to decorative stone for dry creek beds, garden beds, borders, and drainage swales where the rock needs to look good and stay put. It costs two to three times what crushed stone costs because it is sorted and washed, and because the supply is limited to places with river gravel.

Lava Rock

• ✓ Landscaping
• ✓ Garden beds
• ✓ Decorative ground cover

River Rock

• ✓ Landscaping
• ✓ Dry creek beds
• ✓ Decorative borders
• ✓ Drainage swales
• ✓ Water features
• ✓ Ground cover

Lava Rock

• + Very lightweight
• + Excellent moisture retention
• + Decorative appearance

• − Breaks down over time
• − Sharp edges
• − Can scatter easily

River Rock

• + Best-looking bulk stone, natural mixed colors
• + Never decomposes, one-time install
• + Drains fast and rarely clogs
• + Large sizes stay put in moving water
• + Available in sizes from 3/4 inch to 8 inch cobbles

• − Expensive, $40 to $100 per ton
• − Never packs, so it is a poor surface to walk or drive on
• − Heavy and awkward to spread
• − Holds heat in full sun
• − Hard to clean leaves and debris out of

Lava Rock

Typically 3/4"–1.5" sizes. Red or black.

River Rock

River rock is sold by size band: 3/4 to 1 inch (sometimes called large pea gravel), 1 to 2 inch (egg rock), 2 to 3 inch, 3 to 5 inch, and 5 to 8 inch cobbles. Every piece is smooth and rounded. Colors are a natural mix of tan, brown, gray, cream, rust, and black, with regional loads that run mostly one shade. Single-color sorted rock costs more.