Geology Rocks!: In A Sedimental Mood: Rock and Gem Vocabulary

Amethistos means "not drunk" in Greek, and the stone got this name because it was believed to prevent intoxication with alcohol. As a result, wine goblets were often carved from the crystals, and the stone's purple color was said to come from the tears of Dionysus, the god of wine.

Carat comes from keration, Greek for "carob bean." Carob and locust beans were used as weights in the ancient world.

The Greek smaragdus moved into Latin, and from there became the Italian smeraldo and the French emeraude. Emeralds are a brilliant green, and are highly valued.

The geo- in geode is the same as in geology, coming from the Greek root for "earth." Geodes form as bubbles or voids in different types of rock that then slowly fill with crystals as mineral-rich water seeps in over the course of millennia.

One of the three main types of rock, igneous rocks are formed from cooled magma or lava. Ignis is Latin for "fire," which you can also see in words like ignite.

Lapidum means "gem" in Latin. A vivid blue stone that was used to make a precious blue pigment for artists is known as lapis lazuli.

The second main type of rock, metamorphic rock originates as another type but then undergoes major transformation due to heat and pressure. Metamorphic means "change of form" in Greek.

Where emeralds are the most precious green gems, sapphires are the most highly prized blue ones. The word comes from Hebrew sappir, which became the Greek sapheiros and the Latin sapphirus. Sapphires are chemically related to rubies which are bright red and equally valuable. Both are extremely hard, like diamonds, so they have industrial uses as well, for example in watchmaking.

Sedimentary rocks are the third major type. They form from layers and layers of sediment: sand, silt, clay, or seashells that become compressed by the extreme pressures underground or at the bottom of the ocean. Sedere means " to sit" or "to settle" in Latin.