Diamonds
A working index of diamond structure, colour, inclusions, cutting, and the observations that separate description from assumption.
Diamond crystal habits
Octahedra, cubes, and macles preserve evidence of growth before cutting begins.
Diamond crystallises in the cubic system, yet rough crystals present recognisable habits shaped by growth and later resorption. Reading trigons, flattened twins, and curved dissolution surfaces helps explain why two crystals of equal weight can offer very different cutting possibilities.
- Crystal system
- Cubic
- Mohs hardness
- 10
- Common habits
- Octahedral, cubic, dodecahedral
Fancy-colour diamonds
Trace elements and lattice defects can move diamond far beyond the colourless scale.
Fancy colour is assessed by hue, tone, saturation, and distribution rather than by the D-to-Z system. Nitrogen commonly contributes yellow, boron may produce blue, and lattice deformation is associated with many pink and red diamonds; origin-of-colour testing remains a laboratory task.
- Grading framework
- Hue, tone, saturation
- Yellow cause
- Nitrogen-related absorption
- Blue cause
- Often boron-related
Diamond inclusions
Internal features can affect clarity, reveal growth history, and support identification.
Crystals, feathers, clouds, needles, and graining are not interchangeable defects. Their identity, size, number, relief, position, and visibility under standard observation all matter; some also carry geological evidence from deep within the mantle.
- Standard observation
- 10× magnification
- Clarity range
- Flawless to Included
- Scientific value
- Records of growth environment