Question

Consider the following regarding the nature of minerals, evaluate these statements: Which of the statements is/are correct?

1. Minerals must have a definite atomic structure and a specific chemical composition.
2. All minerals found in nature are strictly inorganic substances
3. Coal, Petroleum, and Natural gas are considered organic substances found in the crust.

• A. iii only
• B. i, iii
• C. ii, iii
• D. i, ii

Answer 1

Answer:

B. i, iii

Nature of Minerals and Related Substances

Defining Characteristics of Minerals:

• Minerals are naturally occurring, inorganic solids that possess a definite chemical composition and an orderly internal atomic structure. This ordered structure is what gives minerals their characteristic physical properties, such as crystal form, hardness, cleavage, and color.
• The definite chemical composition means that a mineral will always contain certain elements in a fixed ratio, though some variation (forming solid solutions) is possible within defined limits. For example, Quartz (SiO₂) always has silicon and oxygen in a 1:2 ratio.
• The specific atomic structure refers to the regular, repeating arrangement of atoms within the mineral. This crystalline structure is fundamental to its identity.

Inorganic vs. Organic Substances:

• Statement 2 posits that all minerals found in nature are strictly inorganic. This is the standard definition of a mineral; they are formed through inorganic geological processes.
• However, there are substances found in the Earth's crust that, while naturally occurring and solid, do not fit the strict mineral definition because they are organic in origin.

Organic Substances in the Earth's Crust:

• Statement 3 correctly identifies Coal, Petroleum, and Natural Gas as organic substances found in the crust.
• These are formed from the remains of ancient plants and animals over millions of years under conditions of heat and pressure. Because they are carbon-based and derived from biological matter, they are classified as organic, not minerals in the geological sense.
• Coal is primarily composed of carbon. Petroleum (crude oil) and Natural Gas are complex mixtures of hydrocarbons.
• While they occur naturally, their organic origin excludes them from being classified as true minerals according to the standard geological definition.