What is the Difference Between a Precious and Semi-Precious Stone?

Cut, refined minerals used to make jewelry or embellishments are known as gemstones, and can be either precious or semi-precious. Diamonds, rubies, sapphires, and emeralds are precious, and all others are semi-precious. Interestingly, no difference exists between the two, rather this is a marketing classification invented years ago to give a false sense of value to precious stones.

What are Gemstones?

Precious and semi-precious stones that are used in jewelry are called gemstones. Typically, these stones are cut and refined minerals. However, gemstones are not always composed of minerals. Sometimes precise rocks, or organic resources are considered gemstones and are also used in jewelry and embellishments. Stones that fall under this category include amber and jet.

How are Gemstones Classified?

A person who identifies gemstones is known as a gemologist. Each gem is labeled according to its features using the practical language in the industry. The chemical arrangement is used by gemologists to classify the stones. One such example is that diamonds are made of carbon (C). Inclusions refers to naturally-occurring flaws that exist within the stones.

Because many gems are in a crystalline formation, they can be categorized under a crystal system. Varieties, groups, and species are all used in the classification of gemstones. Furthermore, other characteristics of the stones are used to further segment them, including their dispersion, specific gravity, luster, hardness, cleavage, fracture, and refractive index.

The origin of the terms “precious stone” and “semi-precious stone” was simply a result of a marketing tactic used by people that sold precious stones. This terminology was invented to create the impression that precious stones are more valuable than they actually are. Diamonds, sapphires, rubies, and emeralds are considered precious and all other gemstones are semi-precious.

Which Gemstones are Precious Stones?


A precious stone formed from pure carbon in a crystalline formation that is typically clear and usually colorless is known as a diamond. It’s also the hardest naturally-occurring substance on Earth. It ranks the highest on the Mohs scale of mineral hardness at a 10.


Emerald is a green-colored gemstone. It’s composed of the mineral beryl and derives its green coloration from trace chromium and also vanadium (sometimes). The hardness of beryl is between 7.5 and 8.0 on the Mohs scale.


Ruby is a precious stone which is typically red. The shade can vary from a pale rose to a purple or even dark crimson. The mineral corundum makes up a ruby and is responsible for its red coloration. The hardness of ruby is 9.0 on the Mohs scale.


Also a variety of corundum, sapphire is a precious gemstone. While a traditional sapphire is blue, there are what’s known as “fancy sapphires”, which can be found in shares of green, purple, yellow, and orange. Sapphire is the third hardest natural substance next to diamonds and moissanite with a 9.0 ranking on the Mohs scale.

What are Some Common Semi-Precious Stones?


Pearls are hard objects that are created within the soft tissue of a shelled mollusk or conulariid. Pearls rank between 2.5 and 4.5 on the Mohs scale.

Black Onyx

Considered the anniversary gemstone for the 10th year of marriage, black onyx is chalcedony, a variety of the microcrystalline quartz. The hardness of black onyx is between 6.5 and 7 on the Mohs scale.


A form of silica that is like glass but similar chemically to quartz, is known as opal. Within this mineral, a variable amount of water is found. The hardness of opal ranges from 5.5 to 6.5 on the Mohs hardness scale.

Blue Topaz

Blue topaz is a beautiful stone that comes in a vast range of vivid blue hues. It is a silicate mineral consisting of aluminum and fluorine. Very hard in nature, blue topaz is rated 8.0 on the Mohs scale.


Sodium potassium aluminum silicate is a lustrous mineral known as moonstone. The visual effect, or sheen, is caused by light diffraction from within the micro-structure which is composed of feldspar layers. On the Mohs hardness scale, moonstone is between 6.0 and 6.5.

More about precious and semi-precious gems >>

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