Landscape Rock vs. Gravel
Landscape rock and gravel serve different purposes despite both being "rocks you put on the ground." Gravel is crushed stone — angular edges, structural applications, designed to compact. Landscape rock is decorative — river rock, lava rock, marble chips — chosen for appearance, texture, and permanence. You use gravel under a driveway or as a concrete base. You use landscape rock on top of the soil for beds, borders, dry creek beds, and ground cover.
The Rock Calculator covers eight decorative rock types with accurate density data for each. This matters because rock weight varies by almost 2× across types — a cubic yard of lava rock weighs about 1,500 lb, while the same volume of flagstone weighs over 2,800 lb. Getting the density right is the difference between an accurate tonnage estimate and one that's off by hundreds of pounds.
Unlike organic ground covers like mulch or compost, landscape rock doesn't decompose. A well-installed rock bed with proper landscape fabric underneath will last decades with minimal maintenance. The upfront cost is higher, but the long-term cost is lower — no annual replenishment needed.