Druses and crystal clusters: formation, types, care and choice

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Druse, cluster, cathedral: these words all describe grouped crystals. Differences, formation, care and tips for choosing a fine cluster without surprises.

Key points

Druse	Surface or cavity covered with small, tightly packed crystals
Cluster (amas)	Group of crystals on a single rock base
Common materials	Quartz, amethyst, calcite, celestine, citrine
Hardness	From 3 (calcite) to 7 (quartz, amethyst)
Care	Soft brush; lukewarm water only for quartz and amethyst
Pitfalls	Dyes, glued crystals, citrine made from heated amethyst

Druse, cluster, geode: the words to know

In shops, several words overlap. A druse (a German word) is a crust of small, tightly packed crystals that lines the surface of a rock or the wall of a cavity: it is also called “drusy quartz” or simply drusy. A cluster (amas) is a group of more visible crystals growing together on a common base. A geode is the cavity that contains these crystals (see our page on geodes). A “cathedral” is a trade name for a large half-geode of amethyst set upright: a seller’s term, with no scientific definition.

This page is part of the guide to crystal shapes.

How druses and clusters form

The principle is the same as for points: water laden with dissolved minerals circulates through the rock and deposits its crystals on the walls of a cavity or crack. When the space is very narrow or growth is rapid, thousands of small, tightly packed crystals form: this is the druse. When there is room, a few larger crystals develop in a fan shape: this is the cluster. The crystals of a cluster share the same base and can point in several directions, which gives the look of a “forest” of points.

Druses are not limited to quartz: they also occur in calcite, celestine (a pale blue strontium sulphate, with a hardness of 3 to 3.5), agate, chrysocolla and other minerals. Hardness therefore varies a great deal from one piece to another.

The most common types of cluster and druse

Type	Hardness (Mohs)	Care
Rock crystal cluster	7	Brush, then cloth or lukewarm water
Amethyst cluster or druse	7	Avoid prolonged sun, which dulls the colour
Citrine cluster	7	See below: often made from heated amethyst
Calcite druse	3	No prolonged contact with water, no acids; scratches easily
Celestine cluster	3 to 3.5	Very fragile; handle with both hands

Before cleaning a piece, identify the material: it is the material that determines everything.

Symbolism and uses

Crystal clusters are often presented as objects of “harmony” or “community”, because several points grow together. This is an image that is appreciated in decoration and in popular symbolism, with no proven value. In practice, a cluster serves mainly as decoration: on a coffee table, a piece of furniture, in an entrance hall, or as a visual focus during a calm moment. Some people place small tumbled stones on it, or a tea-light in a glass holder: make sure the flame stays well away from the fragile crystals and does not heat the stone directly.

Care

Dust with a soft brush or a puffer: the spaces between crystals trap dust.
For quartz and amethyst, a lukewarm water bath and gentle brushing are enough. Air-dry or dry with a clean cloth.
For calcite, celestine and druses of soft material, simply wipe dry.
Do not rub the points against each other, as they chip.
Avoid direct sun on amethyst and rose quartz (colour that fades).

Recognising a fine cluster and avoiding pitfalls

Cluster citrine: natural citrine is rare; most yellow or orange clusters sold as “citrine” are heated amethyst. This is an old, accepted treatment, but it must be disclosed. Clues: a white base and points that become more yellow towards the tip; a very uniform, bright orange is often a sign of heating.
Dyes: quartz dyed blue, green or vivid pink. The colours collect between the crystals.
Glued crystals: isolated points added onto a base; glue residue is sometimes visible at the base.
Coatings: “titanium” or “aura” druses with iridescent reflections are covered with a metallic layer deposited under vacuum; the layer can wear away.

To go further, read the citrine entry.

How to choose

Choose according to use and location. For a shelf, a cluster of 8 to 12 cm is well balanced. Look at the base: it must be stable; check whether any crystals are chipped; check the colour in daylight. If you have children or pets, prefer a smaller, lower piece, because the points are sharp. Our pieces are in the raw stones, selenite and geodes section.

Frequently asked questions

What is the difference between a druse and a cluster?

A druse is a layer of small, tightly packed crystals; a cluster is a group of larger crystals on a single base. In the trade, the two words are sometimes mixed up.

Is a cluster of citrine natural?

Rarely. Most yellow clusters sold as citrine are heated amethyst. It is a common treatment; an honest seller will say so.

How do I clean a quartz cluster?

With a soft brush, then lukewarm water and a small brush. Dry it well. Avoid knocks.

Can a calcite druse take water?

Poorly. Calcite is soft (3) and reacts to acids; a dry or barely damp cloth is preferable.

Why are some clusters more expensive?

Size, transparency, the regularity of the points, the rarity of the material and overall condition all play a part. A cluster with many intact points and a fine colour costs more than a chipped fragment.