It forms transparent to translucent colorless, white, pink, and bluish to pinkish grey glassy to greasy crystals.
Its scarcity in eclogite that has been exhumed to the Earth's surface does not reflect its abundance at depth in subduction zones but rather the fact that lawsonite is easily replaced by other minerals.
The substantial amount of water bound in lawsonite’s crystal structure is released during its breakdown to denser minerals during prograde metamorphism.
This means lawsonite is capable of conveying appreciable water to great depths in subducting oceanic lithosphere (Clarke et al., 2006).
Experimentation on lawsonite to vary its responses at different temperatures and different pressures is among its most studied aspects, for it is these qualities that affect its abilities to carry water down to mantle depths, similar to other OH-containing phases like antigorite, talc, phengite, staurolite, and epidote (Comodi et al., 1996).
Lawsonite is a very widespread mineral and has attracted considerable interest because of its importance as a marker of moderate to high pressure (6,000–25,000 bar) and low temperature (300–600 °C) conditions in nature (Clarke et al., 2006).
This mainly occurs along continental margins (subduction zones) such as those found in: the Franciscan Formation in California at Reed Station, Tiburon Peninsula of Marin County, California; schists in New Zealand, New Caledonia, and from other points in the circum-Pacific orogenic belt; the Piedmont metamorphic rocks of Italy; China, Japan, Greece, and Turkey.
Lawsonite has three refractive indices of nα = 1.665, nβ = 1.672–1.676, and nγ = 1.684–1.686, which produces a birefringence of δ = 0.019–0.021 and an optically positive biaxial interference figure.
New metamorphic minerals form through solid-state cation exchanges following changing pressure and temperature conditions imposed upon the protolith (pre-metamorphosed rock).
Lawsonite occurs as inclusions in garnet, as a matrix phase, and in veins, providing a detailed history of subduction and exhumation.