About this stone
Color
BlueVioletPink
Origin
BrazilMadagascarUSAFranceNamibia
Mohs hardness
7
Treatment categories
Natural
Industry-standard treatment
Natural — dumortierite is rarely treated
Mineral chemistry
Aluminum borosilicate Al7(BO3)(SiO4)3O3
Crystal system
Orthorhombic
Stone family
Dumortierite
Common cuts
RoundFaceted Round
Common sizes
4mm6mm8mm10mm
Care notes
Durable (Mohs 7). Mild soap and soft cloth; ultrasonic generally safe.
Related stones
Sodalite, Lapis Lazuli, Kyanite
Frequently asked questions
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What is dumortierite?
Dumortierite is an aluminum borosilicate mineral — chemically (Al,Fe)₇(BO₃)(SiO₄)₃O₃ — that crystallizes in fibrous to columnar masses through high-temperature metamorphism of aluminum-rich rocks. It was first described in 1881 from a deposit near Chaponost, France, and named for the French paleontologist Eugène Dumortier. In bead form it reads as a deep blue with violet undertones, sometimes with visible fibrous texture, and sits at Mohs 7 on the hardness scale. -
Is dumortierite dyed?
Dumortierite is sold natural. The deep blue color comes from trace iron and titanium in the mineral's own crystal structure; it isn't the product of dye, heat treatment, or stabilization. The stone is dense enough that it doesn't take dye the way porous chalcedony, magnesite, or howlite does, and the trade has no tradition of treating it. Every dumortierite strand in Dakota's catalog is untreated. -
What's the difference between dumortierite and sodalite?
Both are deep blue, but the differentiators matter. Dumortierite is harder (Mohs 7 vs. sodalite's 5.5–6), denser blue with violet undertones rather than sodalite's royal blue, and fibrous to columnar in texture rather than granular. Sodalite typically shows prominent white calcite veining; dumortierite shows occasional white quartz host inclusions but no calcite. Sodalite is more common in the bead trade and generally less expensive; dumortierite is the harder, denser, and slightly less familiar choice. -
How durable is dumortierite for daily wear?
Mohs 7 — among the harder stones in the bead trade and substantially harder than sodalite (5.5–6), lapis lazuli (5–5.5), and turquoise (5–6). Suitable for any jewelry application, including rings, bracelets, and necklaces with regular wear. Because the color is intrinsic and the stone is undyed, there is no fade risk; standard soft-cloth-and-mild-soap care keeps the polish stable over years. -
What sizes and cuts does Dakota carry?
Active inventory centers on 8mm, 6mm, and 10mm rounds, with 4mm and 12mm rounds and 5x10–7x16mm rondelles also stocked. Round is the dominant cut. Exact size, cut, and strand specifications appear on each listing — confirm before buying if a strand doesn't specify.