The tumbler index of limestone is a measure of its resistance to abrasion and impact. It is determined by rotating a sample of limestone in a revolving drum with steel balls for a specified number of revolutions. The amount of material that is worn away is then expressed as a percentage of the original weight of the sample.

The tumbler index is an important property for assessing the suitability of limestone for use in construction applications. It is typically specified for crushed stone used in road construction, railway ballast, and concrete aggregate. A high tumbler index indicates that the limestone is more resistant to wear and breakage, while a low tumbler index indicates that it is more likely to disintegrate and break down under load.

The tumbler index of limestone can vary depending on the type and quality of the stone, as well as the specific test conditions used. However, typical values for good quality limestone range from 25 to 35 percent.