GEMMA Quartz and Crystal

Quartz production process

Alpha synthetic quartz is produced in a steel vessel called autoclave using the hydrothermal growth process.
At Gemma’s production unit based in Annecy, France, we concentrate on Top High Quality (THQ) and High Quality (HQ) quartz crystallized in four industrial autoclaves and one laboratory autoclave.
One of the THQ Quartz Production characteristic is its production cycle’s duration of 6 months. Our production capacity is of 2.5 tons of as-grown crystals per year.


Optimized Swept Quartz (OSQ) using a very unique process (under vacuum) is produced in a dedicated oven.

Hydrothermal growth process

The nutrient (lascas) chosen with a low rate of impurities, is placed in a can in the bottom part of the vessel (dissolution zone). The seeds (oriented quartz blades) are hung in the upper part, called the "growth zone".
Both parts are separated by a baffle, a metal plate with a specific number of holes.
The solvent added to the autoclave is sodium hydroxide whose filling percentage determines the operating pressure.
After sealing the vessel, a gradient of temperature is created between the lower and the upper part generating convection currents. The current carries the saturated solution from the bottom to the upper part which is cooled (T2 >T1). The repetition of this process leads to the successive growth of synthetic quartz crystals.
The operating temperature is 350°C and the pressure 1700 bars.
The quality and dimension of crystals depend on seeds specifications (large high quality seeds available) and cycle duration (3 to 6 months cycles).

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