What are Gemstones?

There may be confusion over what constitutes a gemstone. Most people can identify a few gemstones at least – diamond, turquoise, emerald – as they commonly appear in items of gemstone jewelry. A gemstone is any stone which is somehow precious, rare or desirable. But what are the properties of a stone which affords it the ‘gem’ prefix? Is there an objective classification of a gemstone?

In order to understand how we should answer the question of what gemstones are, we need to break gemstones down into four categories: mineral gemstones, rock gemstones, glass gemstones, organic gemstones and possibly even a fifth – synthetic gemstones.

Mineral Gemstones

Most gemstones – diamond, ruby, sapphire, amethyst, garnet etc. - are minerals. A mineral is a naturally occurring substance with a definite, regular atomic structure. That is, a crystalline structure. It is this regular atomic structure that is excellent for gemstone jewelry because a regular atomic structure produces a wonderful interplay with light. It is this interplay with light which can make a mineral gemstone sparkle and scintillate.

Rock Gemstones

A rock is usually an aggregation of minerals, therefore having no regular atomic structure, unlike the mineral. Turquoise is a rock, as is lapis lazuli. As these gemstone rocks have no regular atomic structure, they do not lend themselves to cutting as well as mineral gemstones. This is because, without a regular atomic structure, they are more brittle. Likewise, they are also opaque and will not have the same beautiful interplay with light that mineral gemstones possess.

Indisputably, however, these stones are gems. Turquoise has been valued throughout history and between civilizations for its heavenly color.

As such, rock gemstones are better suited to being cut en-cabochon (that is, half-spheres) and set into a bracelet or bangle.

Glass Gemstones

The gemstone obsidian is a naturally occurring glass. We could simply categorize it with rock gemstones and dispense with this third class of gemstones. However, obsidian bears the classification of being – not a mineral, but – a mineraloid. This is because obsidian is a would-be mineral. It is formed from volcanic lava which cools too quickly for a mineral structure to occur.

Organic Gemstones

Unlike mineral gemstones, rocks or glass, organic gemstones are derived from once-living entities that have petrified. Pearl, for instance, is formed by an irritant lodged in an oyster’s shell-lining. Amber is fossilised tree resin; coral is harvested from marine coral skeletons.

Like rock gemstones, organic gemstones are brittle and are more suited to simple shapes such as beads, chippings, droplets and cabochons.

Synthetic Gemstones

During the Renaissance, goldstone was created by glass-manufacturing monks in Venice when molten copper was accidentally spilled into molten glass. Thus a gemstone was created by a man-made process.

Actually, there is debate whether, due to being synthetic, goldstone should be considered a gemstone at all. I would suggest that synthetic gemstones are discounted and that, by extension, a gemstone must be a naturally occurring phenomenon.

The Definition of a Gemstone

If we take the five ‘types’ of gemstone outlined in this article and use them to shape our definition of what is a gemstone we could say a gemstone is any object – whether stone, fossil or synthesis – that is considered attractive or precious to someone, anywhere in the world.

I would say this definition is unhelpful and excessively subjective. While this holds true I would counsel, that to be a true gemstone, the gem at least has to betray natural origins. We must, therefore, reject synthetic gemstones, though pleasing and attractive they may be.

Yet a gem has to be more than simply of natural origin. Specifically, it has to be a stone or it has to be petrified, i.e., turned to stone from organic matter.

In which case, our four categories of natural gemstones – mineral, rock, glass, organic – all have unique and overlapping qualities that distinguish their gemstone status.

You could say that their overlapping quality is that they achieve their pleasing and precious status by potentially doing ‘something special’ with light and color. This ‘something special’ they potentially do with light and color is what they have. It is how this ‘something special’ comes about that differentiates the types of gemstone.

Mineral gemstones such as diamond and ruby attain beauty through how their crystalline structures influence light and color.

Rocks attain their beauty through how their aggregated components determine color composition and patterns – turquoise’s blueness or greenness is determined by the relativity of its iron and copper composition and so on; the presence of a spider matrix is determined by other impurities.

Note the use of the word potentially. Potentially gemstones do something special. Are we saying that gemstones are only gems once they have been worked and turned into jewelry or other ornaments? I would say yes.

Though light and color are only aspects among many which contribute to the beauty of the gemstone – texture, hardness, scarcity are others that this article has not the scope for – they are of predominant importance.

In raw, unworked, form gemstones are unlikely to reach their maximum potential to do beautiful things with color and light. The ‘gem’ status is acquired only after the stone has been worked by human hand and adulated by human eye.

Our knowledge of ‘gems’ is therefore a-posteriori. It is dependent upon our realization of the full potential a natural stone has for a beautiful display of light and color as jewelry or as ornament. Only then can a gemstone be objectively known.