Folk’s classification of limestones is one of the most commonly used methods of limestone categorization that was introduced by Robert L. Folk and it categorizes limestones based on their composition and texture. This classification is useful when tracing the depositional environments and geological history of limestones.

Folk’s system divides limestones into three main components:

1. Allochems: These are the grains or particles mostly observed in the formation of limestone. They include:
Skeletal grains (bioclasts): Some of the smaller shells, corals, and other organisms recognized in the marine ecosystem.
Ooids: Shapes that are shell-like with concentric circles ranging from inside out.
Pellets: Small, spherical dust, likely to be generated by any of the above-mentioned organisms.
Intraclasts: Limestone chips of a small size or irregular shapes and some of the pieces are split.

2. Matrix: This is a very micro-grain size of the sedimentation material which is made up of infants of calcite in microcrystalline nature known as the micrite that encases the allochems.

3. Cement: The chemical part which is mainly sparite (sparry calcite) formed by the groundwater, cements both the allochems and matrix.

Folk subdivided limestones into classificational types with regard to the kind of the most ubiquitous allochems and matrix or cement. For example:

Oosparite: Limestone with mainly ooids and with sparry calcite cement.
Biomicrite: Limestone that is created mainly from the skeletal part of the micrite mud.
Pelmicrite: Mudstone with lime pellets in the sub-micritic fabric.

This system provides much information on the depositional environments of the limestones and their diagenetic evolution and as such assists the geologists.