Crystal – silicate and quartz minerals that occur naturally in the earth that have a prismatic, crystalline structure in three dimensions. Man-made crystals are a mix of quartz, soda, potash and lead oxide (example: Swarovski).
Hardness – is the crystal or mineral’s resistance to being scratched. The Mohs’ Scale of Hardness is usually used. For example, diamonds are one of the hardest substance in the world, and is classified with a hardness of 1600 on the Mohs’ scale. Below is a list for easy comparison:
10. Diamond (1600)
9. Corundum (400)
8. Topaz (200)
7. Quartz (100)
6. Feldspar (72)
5. Apatite (48)
4. Fluorite (21)
3. Calcite (9)
2. Gypsum (3)
1. Talc (1)
Iridescence – a surface with the ability to change colour depending on light reflection (example: opal, pearl, ammolite).
Opaque – substance that will not let light pass through it.
Translucent – substance that is partially transparent, letting only a little light through.
Baroque – (for Baroque pearls) irregularly shaped pearl.
Freshwater – colourful, irregular-shaped pearls produced by freshwater mollusks (mussels, clams, etc).
Mabe – (or Mobe pearls [Japanese term]) semi-spherical pearls from.
Nacre – the iridescent substance secreted by mollusks to cover an irritant in their shells, which later become pearls.
Oriental pearls – pearls formed without human interaction.