Lab-grown sapphires are genuine gemstones created in controlled laboratory settings. They share the same chemical, physical, and optical properties as natural sapphires, replicating the conditions that produce their mined counterparts.
What Are Lab-Grown Sapphires?
Lab-grown sapphires are true sapphires, not imitations or simulants like glass or cubic zirconia. They are composed of aluminum oxide (Al₂O₃), the same mineral compound found in natural sapphires and part of the corundum family. This identical chemical composition means they possess the same crystal structure and optical characteristics as natural sapphires.
Both natural and lab-grown sapphires score 9 on the Mohs scale, just below diamonds in durability. This makes them highly resistant to scratching and suitable for everyday wear in jewelry. The key distinction between a lab-grown and natural sapphire is its origin: one forms in the Earth, the other is created in a controlled setting.
How Lab-Grown Sapphires Are Made
The creation of lab-grown sapphires involves replicating the geological conditions under which natural sapphires form, though at an accelerated pace. Several methods are employed to synthesize these gemstones, each involving precise control over temperature, pressure, and chemical composition. These techniques allow for the growth of sapphire crystals from raw materials.
The Verneuil, or flame fusion, method is one of the oldest and most cost-effective techniques for producing synthetic sapphires. This process involves melting powdered aluminum oxide in a high-temperature flame, typically around 2000°C. The molten droplets then fall onto a rotating pedestal, gradually cooling and crystallizing to form a cylindrical crystal known as a boule.
Another method is the Czochralski, or pulling, process, known for producing high-quality, clear sapphires. In this technique, a small seed crystal is slowly pulled from a melt of aluminum oxide while rotating. As the seed crystal is withdrawn, a larger sapphire crystal grows from the molten material.
The hydrothermal method closely mimics the natural formation of sapphires by dissolving aluminum oxide in a high-temperature, high-pressure water solution. This process occurs within an autoclave, a sealed environment where temperatures can reach up to 650°C and pressures are significantly elevated. Sapphire crystals then grow around a seed crystal within this solution over an extended period.
Lab-Grown vs. Natural Sapphires
While lab-grown and natural sapphires are chemically and physically identical, gemologists distinguish between them by examining subtle internal characteristics. Natural sapphires often contain various inclusions, such as fine rutile needles (sometimes called “silk”), mineral crystals, or fingerprint-like fluid inclusions, which are remnants of their millions-of-years-long formation within the Earth. These natural imperfections serve as unique identifiers for mined stones.
Lab-grown sapphires, due to their controlled growth, often have different inclusions or are nearly inclusion-free. For example, flame fusion sapphires may show curved growth lines or gas bubbles, unlike natural stones. Hydrothermal and Czochralski methods can yield stones with fewer inclusions or distinct straight growth patterns. Differences in trace elements like iron and titanium are also observable via spectroscopy, as concentrations vary by formation environment.
Color consistency often differs; lab-grown sapphires frequently display more uniform and intense color saturation due to precise control of trace elements. Natural sapphires, conversely, may exhibit color zoning or slight hue variations. Identifying these internal differences requires specialized gemological equipment, such as high-power microscopes.
A key difference is price and market value. Lab-grown sapphires are considerably more affordable, often costing 20-40% less than natural sapphires of comparable quality and size. This disparity stems from the rarity of natural sapphires, which are limited in supply and require extensive mining, versus the controlled production of lab-grown gems. Lab-grown options also appeal to those concerned about environmental and ethical impacts of mining, offering a more sustainable alternative.