An Introduction To Gemstone Inclusions

The Star Ruby owes its magnificent asterism effect to the presence of Rutile needle inclusions.

The history of inclusions in gemstones has come a long way. From being seen as unfortunate imperfections that spoiled a gemstone to becoming unique sources of modern art (yes, that’s right), these inclusions present in gems have also gained particular importance for scientific works. New types of inclusions are discovered with each passing day, making them all the more interesting and exciting to research and talk about, changing the way they are looked upon.

What Are Gemstone Inclusions?

Any material that's trapped inside another mineral is said to be inclusion, while the mineral it's trapped inside is termed as the "host," "host rock," or "host gemstone." Therefore, if one is to find any material inside the body of a gemstone, it's said to be a gemstone inclusion. Inclusions are unique and can be specific to a particular class of gemstone minerals and the geological location where they were mined. At times, an inclusion can even be specific to a particular gemstone mine, too!

How Do Inclusions Form?

Gemstones and crystals are formed inside Earth’s crust amidst extreme conditions. Certain impurities and foreign matter may get trapped inside the crystal during their formation. These materials are particular to the geology of the place. For example, gemstones formed by the metamorphic process usually have solid, crystalline inclusions. In contrast, gems created in sedimentary and igneous rocks often have fluid inclusions containing water or even liquid hydrocarbons like petroleum. Inclusions can also be introduced into the crystal lattice after its formation. A wholly formed gemstone ore may get fractured due to specific geological activity such as an earthquake. Therefore, extra materials around the crystal matrix can get inside these fractures. The foreign matter gets locked in as the gemstone heals due to high pressure and temperature, giving rise to inclusions.

Inclusions And Gemstone Quality

The presence of inclusions has an interesting relationship with the gemstone’s quality. Traditionally, gemstones with fewer inclusions have enjoyed the reputation of being qualitatively superior and have bagged large sums of money in sales and auctions. Even today, precious gemstones like Rubies are highly valued for being “Eye Clean,” a term that denotes the absence of inclusions that are visible to the naked eye.

However, having some inclusions in a gem is desirable since it guarantees its authenticity. Treated, heated, or enhanced gemstones are unnaturally free of inclusions. Fake and lab-created gemstones don't have inclusions, either, and even if some clever minds decide to introduce inclusions in these artificial creations, it's hard to mimic the features of natural inclusions because of their utmost uniqueness.

A highly precious gemstone specimen will become more valuable if it has just the right inclusions, preferably as low as possible. In some cases, the gemstone's beauty can also be enhanced by distinct inclusions that add to its value.

Arguably the most famous Ruby variety, Burmese Rubies have characteristic nested straw-like silk inclusions.

Source: GIA

Some Uses of Gemstone Inclusions

Until today’s time, gem inclusions have not seen much praise. However, they have been found helpful for their scientific and artistic value.

1. Most of the gemstones mined today were formed millions of years ago and carry a part of history in them. These inclusions consist of matter trapped inside the crystals. This matter has clues to the particular time they belonged to. Geologists and scientists can get various clues about how the gemstones were formed, the kind of geological developments Earth has had, and even verify different theories on important subjects like how Earth was formed and its history.
2. Stone inclusions can be used to determine the authenticity of a gemstone with high accuracy. It can predict if the said gemstone sample was heated or enhanced in any way or if it’s entirely a fake product.
3. Since the inclusions are specific to certain geological locations, one can even determine the source location of a gemstone specimen and sometimes even the particular mine.

• Inclusions having insects trapped inside Baltic Amber gemstones are common occurrences.

Different Types Of Inclusions

If there is anything that's more variegated than gemstones, then it's their inclusions. There are numerous varieties of inclusions, and new ones are being discovered regularly. All these inclusions have been classified using various methods for easy understanding.

1 Fluid Inclusions

Fluids like air, water, or even organic/oil-based liquids may get trapped inside a crystal. This results in distinctly visible inclusions, which can be remarkably beautiful, too. Such inclusions are found in crystals and gemstones formed in sedimentary or igneous settings with high temperatures.

2 Mineral Inclusions

Solid-state impurities are the commonest inclusions found inside crystals. These can be minerals like Hematite, Calcite, or Malachite, primary Iron, Calcium, and Copper ores. Such mineral inclusions can result in exciting visual patterns, optical properties, and colors in the gem body.

3 Horsetail Inclusions

Anyone who thinks that inclusions cannot increase the beauty of a gemstone can look at just how mesmerizing Horsetail inclusions are. These are made of Chrysotile mineral and are visible as extremely fine whisks originating from a focal point like a fan or sheaf bundle. Overall, these inclusions appear like a horsetail, hence the name. Many, but not all Ural-type Demantoid gemstones from Russia, Iran, and Italy are known to have these inclusions.

An Ural Type Demantoid, also called Demantoid Garnet, with Horsetail Inclusions.

Source: GIA

4 Hematite Inclusions

Hematite is the mineral name of an Iron ore. When present inside a gemstone, these inclusions give them a metallic luster with a rusty-red, silver-grey to black color. The shape can be needle-like, flaky, or even filamentous and can be found inside many well-known gemstones like Quartz, Garnet, Jasper, etc.

• A Quartz crystal with Hematite inclusions.

5 Mica Inclusions

Mica is a type of silicate mineral with a distinctive sheet-like layered structure. When trapped inside a gemstone, Mica can create various visual effects. Mica Inclusions can have a silver, gold, brown, or green hue and be shaped as tiny flakes or specks inside the gemstone body. These inclusions may also result in optical effects like Asterisms and Adularescence. Gemstones like Kunzite, Muscovite, Schorl, Moonstone, etc., have these Mica inclusions.

6 Calcite Inclusions

Calcite is the mineral name of Calcium Carbonate and is a common inclusion in various gemstones. Calcite inclusions give the gems an attractive appearance due to their variegated color like white, grey, yellow, pink, green, and many more, as well as the optical properties of double refraction and birefringence. These inclusions can also create flashes of light and scintillation, which add to the beauty of their host gemstones.

7 Copper Inclusion

Gemstones can sometimes have copper crystals trapped inside them in their elemental or compound forms. Cuprite, Malachite, and Chrysacolla are some of the copper compounds that are commonly found as inclusions and can give the gemstones various colors depending upon their concentration and level of oxidation. The hue imparted by copper inclusions can vary from ruddy-reddish to oceanic blue, as in the famous Turquoise.

Conclusion

Gemstone Inclusions aren’t the unwanted, wicked imperfections of the historic times. The perspective on them has evolved and changed, and people have started to see their beauty and utility. As in all things, it’s in the imperfections of gems where perfection lies, guaranteeing the exoticness and originality of the piece of gemstone that has witnessed the passage of time and how the world became what it is today. And that’s where the beauty of inclusions in gemstones comes in.

FAQs

What are inclusions?

Inclusions are materials that are trapped inside another material, like gemstones. These inclusions in gemstones can lead to various properties and modify their prices.

How do you identify inclusions in gemstones?

Inclusions may or may not be visible to the naked eye. Various scientific techniques, like Microscopy, X-rays, spectroscopy, etc., can be used to identify gemstone inclusions.

What are the most valuable inclusions?

Horsetail inclusions in Ural type Demantoid Garnets and the rutile needle inclusions in Star Rubies are good examples of some valuable gemstone inclusions.

What are common crystal inclusions?

Calcite, copper, Hematite, etc., are some common crystal inclusions. Depending on the gemstone and where it's mined from, these inclusions can be shaped like needles, feathers, silk, etc.

What are typical inclusions in gemstones?

Some typical gemstone inclusions are Mica, Calcite, Copper, and Iron.