The indigo ray

Where the association came from

Indigo is where blue stops being sky and starts being night. It is not a common mineral colour, and in practice the ray is dominated by one rock and its cheaper look-alike.

Lapis lazuli is not a mineral at all but a rock, mostly lazurite with calcite and pyrite mixed in, which is why good lapis has gold flecks in a deep blue field and looks like a night sky with stars. That resemblance was noticed everywhere it went. It came, and still largely comes, from the Sar-e-Sang mines in Badakhshan, a valley in northeastern Afghanistan that has been worked for over six thousand years, making it plausibly the longest continuously operated mine in the world.

Iolite adds a different oddity. It is strongly pleochroic, meaning it shows violet-blue from one direction and pale yellow-grey from another, so a single crystal changes colour as you turn it. That property is behind the persistent theory that iolite, or possibly calcite, was the Viking sunstone used to locate the sun through overcast sky by detecting polarised light.

What the traditions claimed

Sumer used lapis heavily. The royal tombs of Ur held it in quantity, and it appears in the Epic of Gilgamesh, where tablets and beards are described as being of lapis. Egypt set it in the funerary mask of Tutankhamun and in scarabs and inlay, and connected it with the night sky and with the goddess of the sky.

The pigment story is the one that reaches furthest. Ground and purified lapis produces ultramarine, meaning from beyond the sea, which was the most expensive pigment in European painting from the medieval period until a synthetic version was invented in 1826. Contracts for altarpieces specified the weight of ultramarine to be used and the price of it separately, and it was reserved for the Virgin's robe because it was the costliest thing available.

In Ayurvedic tradition lapis is associated with Saturn as an alternative to blue sapphire, and the same warnings apply. In medieval Europe it was ground and prescribed for melancholy, which is a colour-based argument.

The modern brow-centre reading gives indigo insight, intuition and the inner eye, and this is now the dominant meaning attached to lapis and sodalite alike.

The stones of this ray

• Lapis lazuli (Feldspar & the feldspathoids, Mohs 5.5). A rock, not a mineral, mined at Sar-e-Sang in Afghanistan for six thousand years and ground into ultramarine, once costlier than gold.
• Sodalite (Feldspar & the feldspathoids, Mohs 5.5). Lapis without the gold flecks and at a fraction of the price. Named in 1811, so its lore is entirely modern, mostly about clear thinking.
• Iolite (The gem silicates, Mohs 7). Strongly pleochroic, showing violet-blue one way and pale yellow the other. Proposed as the Viking sunstone used to find the sun through cloud.

Working with the ray

This is the studying ray. If your question is about seeing a situation properly, taking a long view, or making a judgement you have been avoiding, indigo is the honest match, and it is a better fit for that than the blue ray, which is about saying things rather than seeing them.

Lapis is soft at 5.5 and its calcite content makes it vulnerable, so it belongs in a pendant or a pocket rather than a ring worn while working. It should not go in an ultrasonic cleaner and it is damaged by acid, including sweat over long periods.

Sodalite is the practical substitute in every sense: cheaper, harder to distinguish at a glance, and with no gold pyrite flecks. Its lore is entirely modern, since it was only named in 1811, which makes it a useful test case for anyone who wants to see how fast meaning attaches to a new stone.

Colour you can trust

Lapis is faked in three ways. Dyed jasper, sold as Swiss lapis or German lapis, is the oldest imitation and looks flat and evenly blue with no pyrite. Reconstituted lapis is genuine powder bound in resin, which under a loupe looks granular and uniform. Dyed howlite and dyed magnesite also appear.

Genuine lapis has irregular gold pyrite specks, not evenly distributed, and usually some white calcite veining, which lowers the price but confirms the material. Some lapis is dyed to deepen the blue and to hide calcite, and the dye will come off on a cotton bud with acetone.

Sodalite is honest by default, since it is cheap enough that faking it makes no sense, but it is regularly sold as lapis. The distinction is simple: sodalite has white veining and no gold flecks, lapis has gold flecks.

Iolite is sometimes substituted with tanzanite or with synthetic material, and its pleochroism is the identifying test, since turning the stone should shift the colour markedly.