The highest quality coloured gemstones are determined by their colour saturation, hue and depth of tone. Colour saturation refers to colour purity, often referred to as ‘vivid’ or ‘strong’ and the most desirable gemstones display very little grey or brown. Hue refers to the display of pure colour and those stones that are most valuable show very little colour other than the primary colour. Finally, tone represents the depth of colour ranging from light (colourless) to dark (almost black). Tone qualities include light, medium-light, medium, medium dark and dark. Nearly all gemstones today have been treated to enhance their colour and or clarity. Different forms of enhancement include heating and irradiation, in the case of colour, and oil, wax or resin to improve clarity.
Almost all gemstones contain inclusions. The best quality gems are considered to be lightly or moderately included. In addition, some gemstones display fewer inclusions than others and often these inclusions will not detract from the beauty or desirability of the coloured gemstone. For example, emeralds are often highly included and have inherited a romantic term for their inclusions called ‘jardin’(garden), and unless the inclusions disrupt the brilliance of the stone, then they can be virtually ignored.
Coloured gemstones are generally cut to maximize the beauty of their colour. Ideally, all facets should be symmetrical and light should be reflected evenly across the surface of the stone and the gemstone should expose the fewest number of inclusions. Sometimes, stones are cut to display size rather than to display their best colour, especially with more rare stones.
Two gemstones that appear to be the same size may actually have two very different weights. This is because different gemstones have different densities.
Every gemstone has unique characteristics in terms of hardness and durability, and care will vary depending upon individual gemstones. Generally speaking, harsh chemicals, abrasive surfaces and sharp blows can damage even the hardest surfaces. Most gemstones can be cleaned in an ultrasonic or jewellery cleaner, but there are exceptions such as emeralds, pearls, and opals.
The Mohs scale of mineral hardness was devised by Friedrich Mohs in 1812 and is based on the ability of one natural mineral to scratch another. Diamond has the hardness of 10 and is the hardest mineral substance, and is actually four times harder that both Ruby and Sapphire (corundum) which has a hardness of 9.
Stones that have a Mohs hardness of less than 8 are more subject to scratching; harder stones are less likely to be scratched but are still subject to chipping and fracture. When removing dust from soft stones, it’s usually best to rinse them with clean water and dry with a soft cloth. Jewellery should be stored in separate padded compartments or wrapped in soft lint free cloth to prevent scratching, chipping, and entanglement.
When cleaning nonporous gemstones, washing gently with a weak solution of ammonia, rinsing with clean lukewarm water, and drying with a soft lint free cloth is quite effective and safe. With stones harder 7 on the Moh’s scale, it’s safe to do a little gentle scrubbing with a soft toothbrush. A little soaking may be necessary to remove heavier deposits.
Remove your rings before applying lotions or creams.This will help prevent heavy buildup of dirt and oil around your gemstones.
If you plan to do heavy or dirty work with your hands, remove your rings so they will not be subjected to harsh blows, abrasives, or unnecessary dirt. Even diamonds, although they are the hardest substance known to man, can be chipped by a hard blow.
Pearls, coral, and porous stones such as opal, turquoise, or malachite should be kept away from dirty water and oils to avoid discoloration. Wipe them gently with a soft, damp cloth. Do not wear rings containing these stones while washing dishes or similar activities.
Be cautious about the use of ultrasonic cleaners. Some stones are subject to internal stress — tanzanite, opal, emerald, organic gems (such as pearl, coral, and amber), turquoise, lapis, and malachite, and any stone containing major inclusions.
Opal, pearls, coral, amber, turquoise, and many collector gems are quite heat sensitive (both to extremes and to sudden changes in temperature). Do not leave them sitting in hot sunlight, near radiators, or in hot cars.
Birthstone Chart (guideline only)
- January – garnet
- February – Amethyst
- March – Aquamarine
- April – Diamond
- May – Emerald
- June – Pearl, Alexandrite
- July – Ruby
- August – Peridot
- September – Sapphire
- October – Opal, Tourmaline
- November – Citrine, Topaz
- December – Blue Topaz, Turquoise, Tanzanite, Zircon