By Stephan Sawyer
Updated Mar 24, 2022
Grinding stone into powder, or milling, is essential for mineral assays, chemical feedstocks, and construction materials. While most stones are extremely hard, industrially accepted tools—jaw crushers and vibratory pulverizers—make the process efficient, safe, and reproducible.
Start with a hand‑size (fist‑sized) fragment. If the material is larger than a hand, use a sledgehammer or a hydraulic breaker to create a fist‑size fragment (also called a stone chip) that can be fed into a jaw crusher. This first breakage is called a primary crushing stage.
A jaw crusher features a large opening and two heavy steel plates that move in a back‑and‑forth motion. One plate vibrates rapidly against the other, forcing the stone downward until it is reduced to coarse sand or crushed aggregate. Typical jaw crushers can process several dozen pounds of rock per minute and are available for rent from most aggregate equipment suppliers.
The crushed sand is placed into a vibratory pulverizer—a metal housing containing a spring‑mounted platform, an air‑inflated clamp, and a steel disk or “puck.” The platform vibrates at high frequency, causing the disk to break the sand into fine dust. Operate for 1–2 minutes per batch, ensuring the container is filled to at least half its volume (a punch‑in or half‑filled specimen).
Once the vibration stops, remove the container—called a vibratory sieve—and open it to retrieve the powdered material, known as powdered sand or powdered aggregate. Handle the sample carefully; it may be hot due to friction (thermal shock). Place the powder into clean plastic bags or dedicated containers for subsequent analysis or use.
Crushing hard rock generates airborne particles that can damage lungs, eyes, and skin. Always wear:
Because jaw crushers can project shards at high velocity, ensure a safe work area with adequate shielding. The vibratory pulverizer operates at lower throughput—only a few cupfuls per minute—so plan accordingly if you have large volumes to process.
