What kind of technology is this?

Technically, it is inclusion glass with metal additives. Unlike modern effects (such as Aurora Borealis) that are applied only to the surface of the glass via vacuum plating, the "Dragon’s Breath" effect is "locked" directly inside the glass mass itself.

How are the blue reflections created?

This effect is professionally known as opalescence or adularescence (similar to what is seen in moonstone).

Base Material: Specific metals or minerals—most commonly silver or copper compounds—are mixed into molten red glass (usually deep ruby or hot pink) at high temperatures.

Controlled Clouding: As the glass solidifies, these additives form microscopic crystals or layers scattered throughout the main body of the glass.

Tyndall Effect: When light enters the cabochon, it hits these internal micro-layers. The blue part of the light spectrum scatters the most, creating that "inner fire" or bluish flashes that look like a floating haze or lightning inside the stone.

No Backing: Authentic Dragon’s Breath does not have a foil backing (unlike cheap rhinestones). It is transparent or translucent, and the effect emanates from within.

Angle of View: The blue reflections (known as the "blue flash") appear and disappear depending on how you tilt the stone toward a light source.

Historical Context

These cabochons were immensely popular during the Jugendstil (Art Nouveau) and later Art Deco periods. Glassmakers in Northern Bohemia (around Jablonec nad Nisou) were masters at mixing these recipes, which were often passed down through families as closely guarded secrets.

Today, these stones are still manufactured, but the most collectible are the vintage pieces. Due to the glass-melting technology of that era, they possess much deeper and sharper flashes than modern replicas.

Do you plan on using these stones for your own creations, or did a specific piece of jewelry catch your eye?