Any type of stone can be engraved, however there are a few stone types that are typically preferred, due to their properties.
One of the most commonly used stone types for engraved plaques is marble. Marble is a result of the metamorphism of sedimentary carbonate rocks, containing mainly dolomite and limestone. Through metamorphism the recrystallization of carbonate mineral grains occurs, resulting in an interlocking mosaic of carbonate crystals.
Marble has a specific shine, and due to its structure it can remain in good condition for very long periods of time, even under direct action of rain, sunlight etc. On the other hand, compared with other types of stone, marble has a higher degree of brittleness, especially for a few centimeters in the portions where veins meet. Also, in contact with various substances, marble can change colour.
Granite is another type of stone used for engraved plaques, memorials etc. It way sturdier and heavier than marble, a much better choice for outside use, due to the fact that it isn’t easily scratched or broken. Due to the fact that it has larger crystals, it has a coarser and somewhat sparkly appearance. However, even though there is a range of colours and patterns for granite, the array isn’t that wide as for marble. Since granite has superior hardness than marble it’s also more difficult to carve by hand and require power tools.
Both granite and marble are basically heat proof, but both can be stained with various substances, in general oily substances. In terms of price, both granite and marble start at about $55-60 per square foot, but in general, granite, depending on its type, can exceed $200-250 per square foot.