Limestone is a sedimentary rock, with a grainy structure, each grain containing skeletal fragments of marine organism, typically from marine invertebrates such as corals or classes such as Foraminifera. Limestone grains can also contain other inclusions such as silica, and the rock itself can contain sand, silt or clay.
Limestone is a softer type of rock, softer than marble and granite, that’s why it’s quite suitable for sculpting and carving. Most types of limestone have a porous structure compared to other types of stone, and this fact can make it prone to water errosion, and in general, less durable when in contact with other various external factors. However, when it comes to engraved plaques, one can last for ages, placed outside, under various weather conditions, without severe deterioration.
Also due to the porous structure of limestone, it is more susceptible to stains from various substances, even dirt, than other types of stone. However, an engraved stone, placed in vertical position, above ground (evidently outside, not in a kitchen for example), it’s less likely to become stained.
Limestone, although it has superior hardness, is quite sensitive to acids. Therefore, placing an engraved stone in an area with frequent acid rains, or where it can come in contact with acidic substances, can lead to a quick deterioration of the stone.
Typically limestone is much cheaper than marble, granite or other types of stone, since it’s more widespread, and easier to acquire. It generally starts at $7-8 per square foot.