Stones are conventionally distinguished as either precious or semi-precious. It is today considered meaningless – not to mention confusing – to categorise natural stones based on value rather than beauty and rarity. The term ‘natural stone’ covers stones, minerals, crystals and organic gems found in nature.
Gemstones are divided into smaller subcategories based on species and groups. A gem species is a broad gem category that encompasses gemstones that share common qualities. Gemstones of the same species all have an identical chemical composition and structure and can be further divided into different varieties based on factors such as colour, transparency or phenomenon (optical effect).
Quartz is the gemstone species with the largest number of different gemstone varieties linked to it. Gemstones are formed naturally in nature, without human intervention. Most are minerals - natural, inorganic materials with a specific chemical composition – and a small proportion of gemstones are rocks. Additionally, some gemstones are organic, produced by living organisms.
Gemstones are stones formed in nature over thousands of years. The perception of what is considered a precious gem is mainly based on a gem’s rarity – something that has changed throughout history. The amethyst used to be considered a precious stone by many cultures for thousands of years, but a recent discovery of new deposits dramatically decreased the value of the stone, which is now considered semi-precious.
In this chapter we will not distinguish between precious and semi-precious but rather take a look at the overarching category of ‘natural stones’ used in Pandora jewellery.
A gemstone is a mineral or a natural material that has the beauty and durability needed for use as a personal adornment. Some people believe that any stone that meets this definition should be considered as something special and ‘precious’.
Most gems are minerals, however, organic gems are made by animals or plants
Some coloured gemstones are called ‘phenomenal gems,’ meaning that they display striking optical effects. Some of the gems in Pandora’s stone assortment exhibit various phenomena. Moonstone displays a phenomenon known as “adularescence,” which is seen as a cloudy, bluish-white light. White opal displays “play-of-colour,” which resembles a flashing rainbow of colour. Some pearls display “orient” – shimmering streaks of rainbow colours like those seen on a soap bubble.
Gemstone Value Factors
The four diamond quality factors: Carat, Colour, Clarity and Cut apply to coloured gemstones, too. However, colour is by far the most important factor for the beauty of a coloured gemstone. Each gem species and variety has its own colour range as well as a colour that is considered the best within its group.
Gemstone groups are a broader category that encompass minerals from closely related species. The minerals within a group can vary in crystal structure or chemical composition, but will always have common characteristics in at least one of these factors. Some well-known gemstone groups are feldspar, spinel and garnet.
Some gemstone varieties are named simply by adding the colour to the species/group, e.g. blue topaz, pink topaz, etc., while other varieties have earned a distinctive name, e.g. amethyst, carnelian and rock crystal, which are all different colour varieties of quartz.
Ultrasonic cleaners should never be used on natural gemstones as they may crack or otherwise damage the stones. Professional cleaning is recommended for any piece of jewellery with a natural gemstone.
A rough, unpolished sapphire
A polished sapphire.
Gemstones found in nature are true wonders. Each is unique and rare, and the legacy of the long history they possess is unparalleled. Because natural gemstones are formed deep beneath the Earth’s surface over thousands of years, no two are the same and there will be colour variations from stone to stone.
After a stone is sawed and ground to the desired shape, it is polished to a mirror-like finish to aid light reflection from the surface of the stone.
The gemstones used in Pandora jewellery are carefully measured, examined and sorted.
Grinding, usually with silicon carbide or diamond-impregnated wheels, is used to shape gemstones to a desired rough form, called a preform.
Above is an example of an Aquamarine’s span from light to dark.