Precious stones, from underground formation to jewelry creation
Four stones are considered precious on our planet: diamonds, emeralds, rubies and sapphires. Each is unique and distinguished by its beauty, quality and rarity, which determine its value. The colossal amount of work that goes into the creation of jewelry must also be taken into account, as it is in the depths of the earth that rough stones are born. We invite you to discover how gemstones are formed, and the stages they go through to become sublime jewels.
The geological processes of gemstone formation
The formation of gemstones is the result of complex geological processes.
The igneous diamond process
Diamond production begins deep in the Earth's mantle, where temperatures and pressures are extreme. Molten rock cools and solidifies as magma, then is carried to the Earth's surface by volcanic eruptions. When the temperature of these rocks, known as kimberlites, drops, their atoms begin to arrange themselves in an ordered, repetitive crystal lattice structure, until they form diamond.
The metamorphic process for ruby, sapphire and emerald
Ruby, sapphire and emerald follow a process known as metamorphism. This imposes extreme temperatures and pressures on existing rocks, leading to their recrystallization under new mineral compositions.
Ruby and sapphire are derived from corundum, while emerald is derived from beryl.
From the depths of the earth to its surface
Once gemstones have formed in the depths of the earth, their return to the surface depends on various geological events.
The uprising
Geodynamic and tectonic processes bring gems closer to the Earth's surface through uplift when plates overlap or collide.
Erosion
Natural elements like water and wind erode the surface of the earth's crust, exposing lower layers and allowing easier access to gemstone deposits.
The tectonic forces behind gemstone formation
The movement of the Earth's lithospheric plates leads to the collision of continental plates and the creation of subduction zones as one plate moves beneath another. This process creates a high-temperature, high-pressure environment in which diamonds can crystallize, while sapphires, rubies and emeralds emanate from the metamorphism of the affected rocks. As this phenomenon shears the earth's crust, it facilitates the emergence of gemstones.
Gemstone mining
The precious stones now formed are found in the earth's surface crust. Extracting them requires a variety of mining techniques and special equipment, coupled with great care to preserve their integrity. The stones must retain their quality if they are to be used in industry or in the creation of handcrafted jewelry.
Prospecting by geologists
Geologists study the composition of the terrain, taking into account the geological context and history of the area. Magnetometry also helps them identify potential deposits.
In addition, GPR (geo-radar) detects underground faults likely to conceal precious stones. A diamond-tipped core drill extracts samples whose analysis confirms or refutes the geologists' suppositions.
Open-pit mining
Open-pit mining is a two-stage process:
- Excavation to remove the overburden, i.e. the top soil;
- Excavators and bulldozers were needed to extract the precious stones.
Underground mining
Underground mining involves digging shafts and tunnels to access deposits at depth. Blasting and drilling are used to excavate the rock containing the precious stones.
Alluvial mining
When gems are lurking in a riverbed, they are removed by sluices. Gold panning also sifts and washes sediments, separating them from alluvial deposits.
Sorting precious stones
The last step before creating jewelry is to sort the gemstones. They are classified into various categories according to quality, size, weight, color and clarity.
This sorting can be carried out manually by specialists or using state-of-the-art technology reserved for experienced gemologists.
Quality assessment of gemstones
The quality of a gemstone is measured before it is entrusted to the jeweler. In addition to its rarity and purity, its durability also counts for a great deal. Three criteria are studied.
1 - Hardness
Hardness gives the stone excellent resistance to scratches. It guarantees its integrity over time.
Hardness is measured using the Mohs scale, established by the German mineralogist Friedrich Mohs in the XIXe century. Diamond is at the top of the scale with a rating of 10, as it is the hardest mineral. Rubies and sapphires, which can be scratched by diamonds, reach a maximum rating of 9. Finally, emerald is the least hard gemstone, with a rating of between 7.5 and 8 on the Mohs scale.
2 - Stability
The stability of a gemstone is measured by its ability to withstand external aggression: exposure to light, heat, chemicals, etc. If it does, it must not fade, discolor or show any other sign of alteration. If it does, it must not become dull, discolored or show any other sign of alteration.
3 - Tenacity
Finally, the toughness of a gemstone measures its resistance to pressure or shock.
Precious stones in industry
After the long and costly process just described, gemstones can be reserved for professional use. The technology industry relies on gemstones, particularly diamonds, for their unique physical properties, enabling the design of cutting mechanisms, electronic components and precision instruments.
The medical industry uses them to manufacture surgical equipment and precision instruments for scientific research. Finally, some gemstones are reserved for military applications, such as the design of optical components for night vision devices and missile guidance systems.
Working with precious stones to create jewelry
The creation of handcrafted jewelry is the other favored destination for gemstones. It still requires many processes to obtain pieces whose quality will depend on various factors.
Cutting and polishing require both technical precision and artistic skill to bring out the full potential of a gemstone. The piece is then shaped, cut and preformed into a rough configuration. Finally, faceting refines the design.
The art of jewelry making
Every gemstone requires special attention to ensure its sublimity. When creating jewelry, the jeweler's aim is to enhance its brilliance and intensify its colors, while improving its clarity, but never compromising its durability. The value of gemstones is therefore exponential, depending on the work done, the time spent and the talent of the jeweler.
The next step in jewelry creation is the setting. The jeweler selects his style, taking into account the nature of the stones and the aesthetics of the jewel. He chooses the appropriate setting that will highlight the stone, while ensuring its stability on the jewel.
The final stage consists of polishing the gems and fine-tuning the final details.
In conclusion, the creation of handcrafted jewelry from precious stones requires time, passion and talent, as well as state-of-the-art technology and the most sophisticated machinery. This investment, both human and economic, enables the creation of jewels that are as unique as they are exceptional, to the delight of lovers of fine creations.
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