Dumortierite Quartz

Dumortierite quartz is quartz that contains abundant fibrous inclusions of the blue mineral dumortierite, which color the stone in shades of denim, violet, and grayish blue. It is often mottled with white quartz, giving a marbled, denim-like look.

Because the blue color is carried inside a quartz host, the material is hard, durable, and takes a good polish, unlike massive dumortierite by itself. It is sometimes simply called blue quartz.

It is a popular, affordable ornamental and lapidary stone.

Dumortierite is an aluminum borosilicate that forms in boron-rich, high-temperature metamorphic and hydrothermal environments, often in aluminous metamorphic rocks and pegmatites. When dumortierite crystallizes together with or is engulfed by quartz, the result is dumortierite quartz.

The fine blue fibers are dispersed through the quartz, coloring it without compromising the hardness of the silica host. The intensity of blue depends on the density of dumortierite inclusions.

Notable sources include Brazil, Madagascar, the USA (Nevada, California), and Namibia.

Look for a blue to violet-blue, often white-mottled opaque to translucent stone with a vitreous to silky luster, hardness 7, white streak, and conchoidal fracture. The denim-like blue and quartz hardness are key clues.

Distinguish it from sodalite (softer at 5.5-6, more uniform royal blue with white veins) and from lapis lazuli (softer, with pyrite flecks and deeper ultramarine blue). A hardness test separates it from both, since dumortierite quartz resists steel.

The mottled denim color in a hard quartz host is characteristic.

Dumortierite quartz is cut into cabochons, beads, spheres, and carvings, valued as an affordable blue ornamental stone that is harder and more durable than many blue gems. It is also used as a lapis or sodalite alternative.

Massive dumortierite has minor use in manufacturing high-grade porcelain and ceramics, but the quartz variety is mainly ornamental. Metaphysically it is associated with patience, focus, and communication, though such claims are not scientific.

Its durability makes it well suited to everyday jewelry.