silicates
Sodalite
Na4(Si3Al3)O12Cl
- Also known as
- hackmaniteprincess blue
- Crystal system
- cubic
- Hardness
- 5.5–6 on the Mohs scale
- Lustre
- vitreous
- Colour
- Royal blue with white veining
- Where it forms
- In sodium-rich igneous rocks poor in silica, particularly nepheline syenites.
- Chiefly from
- Bancroft, Ontario, CanadaNamibiaBrazilGreenland
Why it is that colour
As with lazurite, sulfur-related colour centres rather than a metal. Some sodalite is tenebrescent — it darkens under ultraviolet light and fades again in daylight, reversibly.
Safety
Safe to handle.
Where it comes from
Abundant and cheap, chiefly from Brazil and Canada. Frequently sold as lapis lazuli, from which it is distinguished by having no pyrite and a softer, more purple-toned blue.
Historical use
Minor. It is a modern ornamental stone, used for tiles, bowls and beads.
Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.
What is attributed to it, and since when
Effectively no history. Sodalite was described in 1811 from Greenland and only became widely available after large Canadian deposits were found in 1891 — reportedly popularised after Princess Margaret of Connaught admired it on a visit, which is where "princess blue" comes from. All meanings attached to it are twentieth-century.
Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.
Sold as this, but not
Worth knowing
The hackmanite variety does something genuinely strange. Fresh from the ground it can be raspberry pink; expose it to daylight and the colour fades to white within minutes; put it under ultraviolet and it comes back. The effect is called tenebrescence, it is fully reversible, and it can be cycled indefinitely.
It is worth noticing which stones attract metaphysical claims and which do not. Hackmanite visibly changes colour in your hand in response to light, which is about as close to a stone doing something as a stone gets, and it is a minor curiosity in the trade. The properties attributed to stones track their appearance and their availability, not their behaviour.
Identity checked against IMA-CNMNC master list, June 2025.