Question

Using the geologic definition of mineral as your guide, determine which of the items on this list are minerals and which are not. If something in this list is not a mineral, explain. a. Gold nugget b. Seawater c. Quartz d. Cubic zirconia

Short answer

Gold nugget and quartz are minerals; seawater and cubic zirconia are not.

Step-by-step solution

Understanding the Definition of a Mineral

A mineral is a naturally occurring, inorganic solid with a definite chemical composition and a crystalline structure. Keeping these characteristics in mind will help us determine which items on the list qualify as minerals.

Categorizing Gold Nugget

Gold nuggets are naturally occurring, have a definite chemical composition (Au), and form in a crystalline structure. Hence, gold nuggets meet all the criteria of minerals.

Evaluating Seawater

Seawater is not a mineral because it is a liquid, not a solid, and does not have a definite chemical composition. It consists of a mixture of water and various dissolved salts, which disqualifies it from being considered a mineral.

Analyzing Quartz

Quartz is a naturally occurring mineral composed of silicon dioxide (SiO2). It has a definite crystalline structure and is widely recognized as a mineral, satisfying all geological definitions.

Examining Cubic Zirconia

Cubic zirconia is a synthetic product made in laboratories. It does not occur naturally, disqualifying it as a mineral despite having a crystal structure similar to minerals.

Key concepts

Minerals

Minerals are fascinating components of the Earth that create the foundation of geology. They are naturally occurring, meaning they are formed by geological processes. Unlike substances that are made artificially, such as synthetic stones like cubic zirconia, minerals are found in nature without human involvement.
Minerals are also inorganic, which means they are composed of elements that do not come from living organisms. While some naturally happening substances can still contain carbon, minerals are solely inorganic.
Another defining characteristic of minerals is that they must be solid under normal Earth conditions. This excludes any liquids or gases from being classified as minerals. Additionally, each mineral has a specific chemical formula which provides consistency in its makeup and properties.
In essence, a mineral must satisfy all the above criteria to be correctly classified. This helps scholars and students alike to distinguish minerals from other geological substances.

Inorganic Solids

Inorganic solids play a critical role in defining what constitutes a mineral. These solids are not composed of living organisms or organic molecules. Instead, they are formed from naturally occurring elements and compounds.
A common misconception is that if something occurs naturally, it is considered a mineral. However, because minerals are defined as inorganic, this effectively differentiates minerals from organic-based materials such as coal, which originates from plant material.
The inorganic nature allows minerals to exhibit specific features that organic materials do not. This includes having a definitive and repeatable internal structure. The strict criteria ensure that only the right substances are classified as minerals, focusing solely on inorganic components.

Chemical Composition

All minerals exhibit a specific chemical composition, a unique combination of elements that form their structure. This exact formula is vital for identifying and classifying a mineral. For instance, quartz is always composed of silicon and oxygen, forming silicon dioxide ( SiO_{2} ), which gives quartz its characteristics.
Chemical composition not only aids in identifying a mineral but also influences its physical properties, such as color, hardness, and reactivity. For example, the pure chemical makeup of gold ( Au ) is responsible for its distinct gold color and malleability.
A definite chemical formula is not flexible, meaning it does not change randomly. This constancy is what helps geologists and educators categorize minerals correctly, providing insight into their formation and potential uses.

• Quartz: SiO_{2}
• Gold: Au

Crystalline Structure

The crystalline structure of a mineral is a key aspect of its identity. It refers to how the atoms or ions are arranged in a repeating pattern at the atomic level, giving the mineral its unique shape and properties.
This ordered arrangement allows minerals to form crystals, which have flat faces, sharp edges, and specific angles that are characteristic of the mineral type. For example, the symmetry of quartz crystals reflects its internal SiO_{2} arrangement.
Crystalline structures vary among minerals, providing a geometry that can range from simple cubic forms, seen in halite, to more complex structures like hexagonal forms found in beryl. These structures are crucial for identification and classification.
Understanding crystalline structures helps scientists determine the potential industrial uses of minerals based on their mechanical properties. It also explains their stability and formation processes.