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