Jewellery (or jewelry in American English) refers to decorative items worn on the body or clothing for personal adornment. These items are traditionally made from precious metals, gemstones, and pearls, though they can be crafted from a wide variety of materials including glass, wood, and shells.
Gemstones can create some quite spectacular optical vistas, depending upon illumination or light source and the stone’s angular facets, and sometimes the optical rainbows created seem to create a type of panoramic effect with rays of multi-coloured light being refracted and reflected in multiple directions, within and without the stone, and forming spectra and naturally appearing points within and outside the stone. The overall effect can be mesmerising.
Goldsmiths
A goldsmith is a metalworker who specialises in working with gold and other precious metals. Goldsmiths were early pioneers in applying solid geometry and perspective methods to represent or instantiate complex three-dimensional shapes, including Platonic/Archimedean solids and polygon combinations, to form attractive jewellery.
Lapidarie
Lapidaries are artisans who cut, polish, and engrave stones, minerals, and gemstones into decorative items, such as cabochons, cameos, and faceted designs, typically excluding diamonds. Originating from the Latin lapis (“stone”), the term refers to both the craftsperson and the art itself, which utilizes techniques like grinding and sawing to enhance a stone’s natural beauty.
Gemstones
The cut of a gemstone dictates how its inherent optical properties—like refractive index, dispersion, and pleochroism—interact with light. Lapidaries calculate specific angles to maximise brilliance, fire, and colour return, while intentionally avoiding light leakage and dull “windows”.
Key Optical Properties vs. The Cut
- Refractive Index (RI): Measures how much light bends (slows down) as it enters a gem. High-RI stones (like diamonds) require precise angles so that light hits the bottom facets and bounces back to the viewer’s eye via total internal reflection.
- Dispersion (“Fire”): The separation of white light into the colour spectrum (rainbow flashes). Facet cuts are designed to enhance this effect by bouncing and scattering these colours.
- Pleochroism: The phenomenon where a gemstone displays different colours depending on the viewing angle. Cutters must carefully orient the stone before faceting to highlight the most desirable colour.
- Chatoyancy (“Cat’s Eye”) & Asterism (“Star”): Exotic optical effects caused by fibrous or needle-like inclusions. These require a smooth, domed cut called a cabochon to properly concentrate and reflect the light
How the Cut Affects Light
Lapidaries juggle beauty against commercial constraints (like carat weight retention) using the following elements:
- Faceting: Translates transparent rough into a symmetrical array of planes that act as a “house of mirrors,” reflecting the optimum amount of light back to the top
- Proportions: If a pavilion is too shallow, light leaks through the bottom (“windowing”). If it is too deep, the centre goes dark (“extinction”).
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