Clear quartz is what the Greeks thought was ice that had frozen so hard it could never melt again. That is where the name comes from. 

Krystallos meant ice, and the word crystal followed it into English still carrying the assumption, which is why lake-clear quartz was called rock crystal for centuries and why the stone is still the one most people picture when they hear the word. 

It took until the seventeenth century for anyone to work out that quartz is silicon dioxide and not water in a permanent state.

The chemistry is simple. Silicon dioxide, the same material as sand and glass, but grown as a crystal with a regular internal structure. Quartz is piezoelectric, so it builds an electrical charge when it is squeezed, and it keeps time. A thin slice of quartz vibrating at a steady rate is what runs every quartz watch and clock, and it has been the working heart of radio and oscillator technology for a century. It sits at seven on the hardness scale, hard enough to scratch glass and hard enough to survive being worn daily, which is why it is used in everything from countertops to lenses.

The deposits are everywhere. Brazil and Madagascar produce most of what reaches the market, Arkansas in the United States gives the famous clear points, and fine material comes out of the Alps, where crystals form in the fissures of the rock and have been collected for centuries. Two things worth knowing about the family. 

First, the coloured stones on this site are all quartz: amethyst, citrine, rose quartz, smoky quartz and the rest are the same mineral with different traces inside it, which is why they share its hardness and its handling. 

Second, a piece that grew freely on both ends rather than being attached to rock at one end is called double terminated, and it is the form collectors pay most for.

Traditionally associated with

Clear quartz has been used for far longer than it has been understood. It is worked into beads and pendants in prehistoric burials, cut into lenses in the ancient world, and carved into spheres and vessels from Rome onwards. 

The Romans used clear quartz for seals and for ornamental spheres, and it was one of the stones ground and worn in the medieval lapidaries. What it did not have until recently is the set of modern associations now attached to it, which are a twentieth-century development. 

In modern practice it is kept alongside other stones and used as the piece the rest are set with.

How I'd keep it

Quartz is one of the easier stones to own. Warm water and a little mild soap are fine, and a soft brush will not harm it. Keep it away from acids, bleach and household cleaners, which will leave a dulled residue on the surface. A cluster should be dusted rather than soaked if it is a piece with fine points, since water in a tight crevice is slow to dry. It is stable in sunlight and does not fade. The one caution is that quartz is hard enough to scratch softer stones, so a cluster or a sphere kept in a drawer with calcite, malachite, selenite or aragonite will mark them. Give it its own spot.

What to watch for

Clear quartz is rarely faked outright, because glass is easier and cheaper to spot, but it is regularly mislabelled. 

Smoky quartz, citrine, amethyst and the aura treatments are all sold under names that obscure the fact that they are quartz, which matters when a price is attached to the name rather than the stone. 

Glass is the genuine lookalike, and the tells are bubbles inside the material and rounded edges at the points, since glass does not grow the flat crystal faces quartz does. 

Dyed and heat-treated material is common with the citrine and smoky material particularly, and a piece described as natural citrine at a low price is almost always heated amethyst. And because clear quartz is abundant, pay for the size, clarity and the form of the piece rather than for the name.

In the shop

The Clear Quartz Cluster at £175 is one of the largest pieces I carry, and it is a one-off, so the cluster in the photograph is the one that arrives. There is also the Clear Quartz Skull at £30, which is carved from a single piece.

Free UK shipping on orders over £50. Everything is sent from Luton, and collection is available if you're local.