Color and Finishes for Limestone
There are many factors that contribute to limestone’s color, veinings, clouds, mottlings, and shadings. These substances contribute in small amounts during the limestone’s formation. These include iron-bearing minerals, clay, and organic material thought to be residual from the soft parts of tiny marine animals. Most of these dark materials are found between calcite crystals or the shell materials, and some shells and calcite crystals are darker than others. Colors of biologic inclusions are strongly affected by the environment of deposition; for example, whether the bottom conditions are aerobic or anaerobic. Iron oxides make the pinks, yellows, browns, and reds. Most grays, blue-grays, and blacks are of bituminous origin.
Texture of Limestone
Limestone receives it’s distinct texture from a variety of different elements. The term “texture,” as applied to limestone, means size, degree of uniformity, and arrangement of constituent minerals. Limestone contains a number of distinguishable natural characteristics, including calcite streaks or spots, fossils or shell formations, pit holes, reedy formations, open texture streaks, honeycomb formations, iron spots, travertine-like formations, and grain-formation changes. One or a combination of these characteristics will affect the texture.
Finishes of Limestone
Limestone surfaces may be finished in a number of different ways.
Some typical finishes are:
Honed: A satin smooth surface with little or no gloss.
Smooth: Smooth finish, with minimum of surface interruption.
Plucked: A rough texture. Abrasive: A flat, non reflective surface.
Sawn: A comparatively rough surface; can be chat, shot, sand, or diamond sawn.
Polished: Mirror gloss, with sharp reflections.
Bush-hammered: textured surface that varies from subtle to rough.
Thermal (Flamed): Finish produced by application of high-temperature flame to the surface. Large surfaces may have shadow lines caused by overlapping of the torch. This finish will vary in texture and depth between different types of limestone, as the finish is largely dependent upon the limestone structure of the stone. The thermal method is not commonly used on limestone.
Antiqued: A finish that replicates rusticated or distressed textures.
Tumbled: A weathered, aging finish created when the stone is tumbled with sand, pebbles, or steel bearings. Other finishes such as machine tooled are available and it should be noted that not all finishes may be applicable to all limestones. Some stone finishes can affect strength and durability. Hammered and thermal finishes may reduce a stone’s thickness, making it more vulnerable to weaken from exposure to freezing and thawing cycles. The type of finish desired may affect the final cost. For further information on cost differences between various finishes contact MIA member companies.