A masonry mortar that is composed of hydrated lime or lime putty and water with sand or marble dust. Lime mortar was the primary mortar used for masonry before the invention of Portland cement (Bucher 1996). Nowadays it is not often used because it hardens at a very slow rate. It has been used as a plaster for fresco (Mayer 1969). Synonyms: lime-sand mortar. Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated); Bucher (1996); Mayer (1969). [J. Cassar, R. de Angelis]