Raw black diamonds, distinct from their faceted counterparts, possess a unique appeal. Understanding their characteristics is key for initial identification. This guide aims to illuminate the properties of raw black diamonds, helping to recognize them and differentiate them from other materials.
Understanding Raw Black Diamonds
Raw black diamonds, also known as carbonados, are an unusual form of diamond. Unlike typical diamonds which are single crystals, black diamonds have a polycrystalline structure, meaning they are composed of many tiny diamond crystals bonded together. This structure contributes to their opaque, dark appearance, which ranges from deep charcoal to a muted brown-black. The polycrystalline nature of raw black diamonds affects their properties significantly, making them tougher than single-crystal diamonds, though they can also be more porous. Their color is attributed to numerous dark mineral inclusions, such as graphite, magnetite, and hematite, dispersed throughout their structure. These geological processes, occurring deep within the Earth under immense pressure and heat, give black diamonds their distinctive characteristics and contribute to their rarity.
Key Visual Cues for Identification
The surface texture of raw black diamonds is often rough, bumpy, or granular, differing significantly from the smooth, polished facets of cut diamonds. This unrefined texture is a hallmark of their raw state. Raw black diamonds typically exhibit a greasy to sub-metallic luster. This sheen is distinct from the brilliant sparkle seen in clear, faceted diamonds, as raw black diamonds absorb most light.
Their color should be a consistent, deep black, although some may present with very dark gray undertones or subtle speckles. True raw black diamonds are completely opaque, meaning light should not pass through them at all. Their shape is often irregular, appearing amorphous or as rough octahedral forms, unlike the precise geometric cuts of finished gemstones.
Simple Home Identification Tests
Diamonds are the hardest known natural mineral, ranking 10 on the Mohs scale. A genuine raw black diamond should scratch materials like quartz (Mohs 7) or glass, while remaining unscratched. Raw black diamonds possess a higher density than many common simulants, making them feel noticeably heavier. Diamonds have a specific gravity of approximately 3.52. This density difference can be assessed by comparing the stone’s weight to a known simulant of similar size.
Being opaque, raw black diamonds primarily absorb light and will not display the internal fire or sparkle of faceted, clear diamonds; they will appear much duller. Diamonds are also excellent conductors of heat. A quick test involves breathing on the stone; a genuine diamond will disperse the fog almost immediately, usually within one to two seconds, feeling cool to the touch.
Distinguishing from Common Look-Alikes
Black moissanite, often lab-created, has a Mohs hardness of 9.25 to 9.3. It often exhibits a distinct rainbow-like “fire” or brilliance not seen in opaque black diamonds. Black spinel, a natural gemstone with a Mohs hardness of 8, has a vitreous or glass-like luster and can appear brilliant, lacking the metallic sheen of black diamonds.
Black onyx, a variety of chalcedony quartz, has a Mohs hardness ranging from 6.5 to 7, making it softer than diamond. It often presents a waxy or vitreous sheen and may have a banded appearance.
Black cubic zirconia (CZ) is a synthetic material with a Mohs hardness of 8.5, but it has a lower density than diamond and can display a more artificial sparkle. Hematite, an iron oxide mineral, has a Mohs hardness between 5 and 6.5 and exhibits a metallic luster. It is also known to leave a reddish-brown streak when rubbed on an unglazed ceramic surface and can sometimes be magnetic.
When to Seek Professional Verification
While home tests provide useful preliminary indications, they have limitations. For definitive identification and valuation, particularly for significant pieces, professional gemological appraisal is essential. Gemologists possess specialized equipment and expertise to accurately assess gemstones.
They use tools such as diamond testers that measure thermal conductivity, advanced microscopes to examine internal structures and inclusions, and refractometers to measure how light passes through a stone, though refractometers are less useful for opaque black diamonds. Professionals also employ spectroscopes to analyze a stone’s light absorption patterns and specific gravity liquids to determine density.
These scientific instruments, combined with a gemologist’s trained eye, can distinguish between natural raw black diamonds, treated diamonds, and various simulants with high accuracy. Consulting a certified gemologist offers the only certain method to confirm authenticity.