Dumortierite is an aluminum boro-silicate mineral, Al7BO3(SiO4)3O3. This metamorphic stone forms deep in the earth under high temperature and pressure. Replacing the aluminum content with iron as it is forming naturally causes the stone to exhibit the characteristic blue color. If formed with titanium and magnesium deposits, it can be found as a pink stone.
The color range is brown, red, green, light to dark blue, lilac, violet, and pink, the latter two being the rarest. Often occurring with ochre colored patches from the iron. Even rarer are the clear quartz stones with inclusions of dumortierite, which occur as bright needles or spikes in the quartz.
Occasionally may be pleochroic, i.e., will change color at different viewing angles in polarized light. This effect may be difficult to see If the stone is opaque.
Low quality mineral deposits are generally not uncommon, since it is mined for industrial uses involving heat-resistant glass and ceramics, like integrated circuit components, insulating tiles, or spark plugs. However, visually appealing stones that can be used in lapidary are more difficult to find. Could be mistaken for sodalite or lapis lazuli, but it's a heavier, harder stone, with Mohs hardness 7.5 - 8 and specific gravity of 3.3 - 3.4. A very durable stone, it cannot be synthesized. However, imitations have been attempted and are prevalent in the international market.
Strand is approx. 15 in.
Shipping estimate: 3-5 weeks