What’s the difference between a gem and a mineral?

Some, but not all, minerals are gems, and some, but not all, gems are minerals.  Confused?  Good, then we’re ready to start.

Amethyst is both a mineral and a gem

A GEM has the following properties:

• Rarity
• Beauty
• Durability

A MINERAL has these properties:

• Inorganic
• Naturally occurring
• Set chemical formula or range of formula
• Solid with unique crystalline atomic structure

(A rock is composed of more than one mineral although a large mass of a single mineral can also be called a rock.)

In general, the properties for gems are much more loosely defined than those for minerals.  Let’s look at some of these properties.

Rarity: Rarity describes how common a gem is and can change as gem deposits are mined out or new sources found. Rarity is also relative to each individual gem; for instance, large inclusion-free amethysts are common, but large inclusion-free emeralds are extremely rare. Generally, the “cleaner” and larger the gem, the rarer and therefore more expensive it will be.

Beauty: Not everyone agrees on what is beautiful, but there are gems for just about everyone’s taste.

Durability: Durability is a gemstone’s ability to withstand wear, heat, and chemicals. Durability consists of three properties: hardness, toughness, and stability. Hardness means how well a gemstone resists scratches and abrasion. Toughness describes how well a gemstone resists breaking and chipping. Stability means how well a gem resists chemicals and temperature changes. (http://www.gia.edu/diamond-care-cleaning)

Inorganic: Not a previously living plant or animal.

Naturally occurring: Not made by humans.

Set chemical formula or range of formula and unique crystalline atomic structure: This is what creates specific crystal shapes and consistent properties for a given mineral.

Examples of gems that are not minerals:

• Pearls, fossils and amber (“organic” gems)
• Any synthetic gem (not naturally occurring)

Examples of minerals that are not gems:

• Gypsum, mica (not durable)
• Milky quartz (not rare)
• Hornblende (not beautiful as a gem)

When you look at a piece of gem jewelry, consider how these factors came together when you admire its beauty!