Which of the following is not true about minerals? A They always include oxygen and silicon. B They are naturally occurring materials. C They each have unique properties. D They have a crystalline structure.
The correct answer and explanation is:
The correct answer is A. They always include oxygen and silicon.
Minerals are naturally occurring inorganic substances with a defined chemical composition and crystalline structure. However, it is not true that all minerals contain oxygen and silicon. While many minerals do include oxygen (such as oxides or silicates), not all of them have these elements. For instance, minerals like gold (Au), copper (Cu), and sulfur (S) do not contain oxygen or silicon.
B. Naturally occurring: Minerals form naturally in the Earth, typically through geological processes such as cooling of magma, evaporation, or precipitation. They are not synthetic or man-made. This makes “naturally occurring” one of the defining characteristics of minerals.
C. Unique properties: Every mineral has distinct properties such as hardness, color, luster, and chemical composition. These characteristics help in identifying and classifying minerals. For example, diamonds are extremely hard due to their crystalline structure of carbon, while talc is soft.
D. Crystalline structure: Minerals form in a specific arrangement of atoms, creating a regular, repeating pattern known as a crystal lattice. This crystalline structure is another defining feature of minerals. Even if the mineral is too small to see the crystals with the naked eye, its atomic structure still follows this orderly arrangement.
Therefore, while oxygen and silicon are common elements found in many minerals (especially in silicates), they are not universally present in all minerals.