Rockhounding in Arizona – What Rocks You Can Find and Where

Quartz

Hardness: 7

Streak: White

Chemical Formula: SiO₂

Quartz is one of the most common minerals found in the Earth’s crust. While it is usually colorless and transparent, quartz can also be found in a wide variety of colors and a range of opacity. These varieties generally have their own name such as rose quartz, amethyst, smoky quartz, and citrine.

Quartz can also be found in cryptocrystalline varieties, or quartz that is made up of microscopic crystals. These varieties include chalcedony, agate, and jasper.

Agate

Streak: White

Hardness: 7

Chemical Formula: SiO₂

Agate is a common form of chalcedony, a microcrystalline form of quartz. It’s banded, colorful appearance has lead to its widespread use throughout human history.

Most varieties of agate are named for its visual appearance, such as fire agate which has inclusions of red or brown hematite. Agate can also vary in its banding appearance, some agates have a dendritic habit or lace-like patterns with eyes, swirls, and other patterns.

Because this mineral is a form of quartz, it’s hardness lends itself to uses not commonly associated with such visually appealing minerals. Agate has been used to create precision pendulums, mortars and pestles, and fine knife-bearing edges for laboratory balances.

Photo: Agate by James St. John is licensed under the Creative Commons Attribution 2.0 Generic license.

Turquoise

Turquoise is Arizona’s most important gem material. This gem ranks top in value per production and is the most widely known of Arizona’s gemstones. Most collectors consider American Turquoise to be the finest in the world and Arizona to be the state that the best blue Turquoise comes from.

Photo: Turquoise Apache Junction by Marie-Lan Taÿ Pamart is licensed under the Creative Commons Attribution 4.0 International license.