Classification and Characteristics of Precious and Semi-Precious Stones
Natural and synthetic gemstones, while sharing similar appearances, have distinct origins and formation processes.
Origin and Formation
Natural gemstones are formed deep within the Earth’s crust or through metamorphic processes over millions of years under natural environmental conditions. On the other hand, synthetic gemstones are created in laboratories using controlled scientific techniques that mimic natural growth processes. For instance, the Czochralski method is used for alexandrite synthesis, while high-pressure high-temperature (HPHT) and chemical vapor deposition (CVD) are employed for diamond synthesis.
Chemical Composition and Physical Properties
Synthetic gemstones have the same chemical composition and crystal structure as their natural counterparts, making them genuine gems, not imitations. This means that synthetic diamonds are real diamonds, just lab-grown. However, because they are grown in controlled environments, synthetics often display fewer inclusions or flaws and can be more visually "perfect." Natural stones typically have characteristic inclusions, fissures, or growth patterns caused by geological conditions.
Visual and Clarity Differences
Natural gems often contain internal inclusions visible under magnification, while synthetic stones usually have higher clarity, often appearing flawless or nearly so. Some synthetic processes produce stones free of inclusions entirely, such as synthetic alexandrite grown by the Czochralski method, which contrasts with natural alexandrite that might display tiny crystals or fissures.
Cost and Availability
Synthetic gems tend to be significantly less costly due to faster production times and absence of mining rarity, making them accessible alternatives to expensive rare natural stones like alexandrite or diamonds.
Identification and Testing Challenges
It is often difficult to distinguish between natural and synthetic gemstones without specialized equipment. For instance, synthetic diamonds require advanced electronic testers costing hundreds or thousands of pounds and gemological expertise to differentiate from natural stones. Gemological testing—examining refractive index, inclusions, growth patterns, pleochroism, or spectroscopy—is essential to identification.
Additional Notes
Synthetic gemstones replicate natural stones chemically and physically, unlike simulants like cubic zirconia or moissanite which only look like gemstones but have different chemistry and properties. Synthetic stones aim to produce a product identical to natural in terms of crystal structure and chemical makeup, but grown faster, cleaner, and more uniformly.
Other Factors to Consider
Understanding a gemstone's hardness can help make informed decisions about its practical applications. The Mohs scale, a standard for gauging a gemstone's hardness, places diamonds as the hardest known natural material (Mohs scale 10) and talc the softest (Mohs scale 1).
Spectroscopy is a technique used to identify the unique "spectral fingerprint" of each mineral, allowing for the accurate identification of a gemstone's composition.
When buying a gemstone, it's important to check the 4Cs—Carat, Cut, Color, and Clarity—consider the Mohs scale of hardness, ask for certifications, and be aware of the gemstone's specific care and maintenance requirements.
Traditional methods of gemstone classification include color, hardness, and location of origin. However, modern technology provides more precise methods for gemstone classification, such as spectroscopy and X-ray diffraction. Understanding a gemstone's crystal structure can be vital for identification and can even reveal whether the gem has been treated or altered in any way.
Density and specific gravity are measurements that provide insights into a gemstone's composition and quality. Luster, what gives a gemstone its 'sparkle', is a critical factor in determining a gem's beauty and value.
Carbonate gemstones are generally softer and more porous than other gem families, making them less suitable for high-impact jewelry like rings. On the other hand, they are budget-friendly options, known for their affordability, but not a lack of beauty or quality.
Rubies are a variety of the mineral corundum, just like sapphires. They have a vibrant red color due to trace amounts of chromium and score a 9 on the Mohs scale. Emeralds belong to the beryl mineral family and get their green color from trace amounts of chromium and vanadium. They are relatively soft compared to diamonds, usually scoring between 7.5 and 8 on the Mohs scale.
Calcite and aragonite are two examples of carbonate gemstones. Silicates are the largest gemstone family and are known for their complex crystal structures and durability.
Rubies are generally classified based on their color, clarity, cut, and carat weight, with the most valuable rubies having a vivid, medium-dark red tone. Emeralds are often classified by their color, clarity, cut, and carat weight, but inclusions in emeralds are often considered acceptable and can even add to their character.
Natural gemstones are generally more valuable due to their rarity and unique formations, while synthetic gemstones are less expensive and can be flawless. However, the value of a gemstone is not solely determined by its origin but also by its quality, rarity, and the demand in the market.
[1] https://www.gia.edu/synthetic-diamonds [2] https://www.gia.edu/synthetic-gemstones [3] https://www.gemstones.org.uk/synthetic-gemstones [4] https://www.diamond.net/education/synthetic-diamonds [5] https://www.diamondfacts.org/synthetic-diamonds/
Synthetic gemstones, while sharing the same chemical composition and crystal structure as natural gemstones, can provide health-and-wellness benefits through their integration into wellness-focused jewelry and accessories due to modern science's ability to grow them cleaner and more uniformly. Additionally, understanding the nuanced trace elements in gemstone compositions, especially for colorful gemstones like rubies and emeralds, can offer insights into the nutritional health of the Earth during their formation and contribute to the growth of science in the field of earth science.
