Limestone Grades & Classifications

Grade Descriptions

The Indiana Limestone Institute grade classifications are based on the degree of fineness of the grain particles and other natural characteristics which make up the stone. The structural soundness of each of the grades is essentially identical.

As a natural product, Indiana Limestone contains at least a few distinguishable calcite streaks or spots, fossils or shelly formations, pit holes, reedy formations, open texture streaks, honeycomb formations, iron spots, travertine-like formations and grain formation changes. However, through the years, one of the pleasing features of Indiana Limestone which has made it adaptable to the various architectural styles is that, as these do not exist in large, noticeable concentrations from stone to stone, one piece looks very similar to another with no discernible pattern of these natural characteristics. For this reason, Indiana Limestone does not lend itself to pattern blending as do stones which have characteristics such as specifically pronounced veining which exists from stone to stone.


Fine to average-grained stone having a controlled minimum of the above characteristics.


Fine to moderately large-grained stone permitting an average amount of the above characteristics.


Fine to very coarse-grained stone permitting an above-average amount of the above characteristics.


An unselected mixture of grades 1 through 3 permitting both the buff and gray colors

Important Notes

It is advisable that all stone for each project be furnished from a single quarry. This should result in the best possible color control.

VARIEGATED stone will contain an uncertain percentage of the individual stones containing both colors while other stones may be all buff or all gray. When both colors occur within a single stone, the dividing line is usually readily discernible, and may be horizontal, vertical, diagonal and/or curved. The degree of contrast between the two colors, whether they appear in a single stone or in stones of solid individual colors, may be readily apparent or nearly indiscernible. Neither fabricator nor erector will attempt to control the location in the building of panels or individual stones according to their natural variations of color or texture.

Since it is impossible to show all natural characteristics by sample, the approval sample should be used only as a general guide to final building appearance. Characteristics noticeable at arm’s length will appear differently when viewed in the building at normal distance.

As stone sizes increase, GRADE selectivity decreases until it may no longer be possible to classify SELECT or STANDARD grades according to ILI Classifications. Color, stone size and project size thus become the governing criteria. Designers and specifiers are urged to consult ILI or its member companies for specific current information.

Note: Large-scale samples, including sample walls (mockups) complete with connections and joint closures, can be helpful in selecting stone color and quality. These constructions should be preplanned and included in bid specifications where their additional expense is warranted.