Hardgrove test

geology

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 29, 2026

Quick Summary

The Hardgrove test is a method used in geology and coal utilization to measure a coal's resistance to crushing, known as its grindability. This test involves grinding a prepared coal sample in a standard laboratory mill. The percentage of coal that passes through a 200-mesh sieve (74 micrometers) is used to calculate the Hardgrove grindability index (HGI). This index helps determine the appropriate size of grinding equipment for coal-preparation plants. Factors like moisture and ash content influence grindability, with lignites and anthracites generally being more resistant to grinding than bituminous coals. Grindability itself refers to the capacity for or resistance to being ground.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

2 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

coal utilization
Grindability
…for assessing grindability is the Hardgrove test, which consists of grinding a specially prepared coal sample in a laboratory mill of standard design. The percent by weight of the coal that passes through a 200-mesh sieve (a screen with openings of 74 micrometres, or 0.003 inch) is used to calculate…
Read More
…for assessing grindability is the Hardgrove test, which consists of grinding a specially prepared coal sample in a laboratory mill of standard design. The percent by weight of the coal that passes through a 200-mesh sieve (a screen with openings of 74 micrometres, or 0.003 inch) is used to calculate…
Read More