A Guide to Ornamental Gemstones

Ornamental gemstones are non-transparent minerals and rocks, with a variety of colours, textures and patterns. On the Mohs scale, the majority of these stones have a hardness of seven or less.

The following list takes a look at what makes ornamental gems valuable and attractive:

  • Chalcedony – Has fine grains and a waxy sheen. Chalcedony varieties include green Chrysoprase, brownish-red to orange Carnelian, black-and-white Onyx, and brown-and-white Sardonyx.
  • Jasper – Has a rough, grainy form. Its colour comes from iron inclusions.
  • Aventurine – Translucent and produces aventurescence (optical reflectance), with green, brown and blue colours.
  • Bloodstone – Also called heliotrope. It’s bright to dark green with red spots.
  • Agate – Has concentric layers, with various colours and patterns. Fire agate has iridescent layers. Dendritic agate is whitish-grey, with fern-like patterns.
  • Dumortierite – A unique, deep blue colour.
  • Geodes – Rock formations with crystal cavities.
  • Tiger's eye – Gold, brown or green, with chatoyant stripes.
  • Pietersite – Has swirling blue, red, gold and brown colours.
  • Lapis lazuli – Deep blue colour, with pyrite spots and streaks. Used since ancient times.
  • Sodalite – Blue with violet tints and white calcite veins.
  • Malachite – A popular and polished stone, with green circular bands.
  • Chrysocolla – Found in a combination of colours, particularly blue and green.
  • Turquoise – Pale blue colour. Popular and valued since ancient times.
  • Howlite – Greyish-white vein patterns, also known as white turquoise.
  • Rhodochrosite and rhodonite – Pale-pink to rose-red colours. Rhodochrosite has alternating zigzag stripes and circular patterns. Rhodonite has black-and-brown patch and vein patterns.
  • Moonstone – Produces adularescence, a shimmering light effect.
  • Amazonite – A green variety of microcline. It takes its name from the Amazon River, Brazil.
  • Labradorite – Produces a schiller effect, with metallic shimmers.
  • Sunstone – Displays a spangled appearance.

Ornamental gemstones are usually soft and vulnerable to damage. They can also be enhanced, fake or synthetic.

Source: http://www.jewellermagazine.com/Article.aspx?id=2871&h=Gemstones-of-d%C3%A9cor%3a-ornamental-gems

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