definition
A mineral of alkaline igneous and plutonic rocks that are low in silica, of the chemical composition of sodium aluminum silicate with chlorine, Na4Al3Si3O12Cl. Pink sodalite is sometimes called hackmanite. Sodalite and lazurite form the sodalite Group of silicate minerals.
The felspathoid minerals, sodalite, haiiyne and nosean, which crystallize in isometric dodecahedra, are very frequent components of the phonolites; their crystals are often corroded or partly dissolved and their outlines may then be very irregular.
From these rocks in the Ottawa valley are quarried or mined granite, marble, magnificent blue sodalite, felspar, talc, actinolite, mica, apatite, graphite and corundum; the latter mineral, which occurs on a larger scale here than elsewhere, is rapidly replacing emery as an abrasive.
Blue gemstones such as sodalite combined with red jasper can look fantastic.