Question

Quartz is a crystalline variety of: (a) Silicon (b) Silica (c) Sodium silicate (d) Silicon carbide

Short answer

Quartz is a crystalline variety of silica (option b).

Step-by-step solution

Understanding Quartz

Quartz is a mineral composed primarily of silicon and oxygen atoms. It is known for its crystalline structure and is one of the most abundant minerals on Earth's crust.

Terminology Clarification

The terms 'silicon' and 'silica' are often confused. 'Silicon' is a chemical element with the symbol Si, while 'silica' refers to silicon dioxide (SiO₂). Silica is a compound comprising silicon and oxygen, and it is found in nature as quartz.

Analyze Each Option

- Option (a) Silicon: Silicon itself is not crystalline; it's a separate element. - Option (b) Silica (SiO₂): This is the chemical compound that forms the crystalline structure of quartz. - Option (c) Sodium silicate: This is a compound composed of sodium, silicon, and oxygen, not related to quartz. - Option (d) Silicon carbide: This is a compound of silicon and carbon, typically used as an abrasive, not related to quartz.

Choosing the Correct Answer

Based on the analysis, quartz, being a crystalline form of silicon dioxide, matches with option (b) Silica (SiO₂). Silica is the fundamental component of quartz.

Key concepts

Silica

Silica, scientifically known as silicon dioxide (SiO₂), is a fascinating compound predominantly composed of silicon and oxygen. It is found widely across the globe.
This compound forms the basis of many minerals, including quartz. One common occurrence of silica sees it forming tightly packed units within crystals. These formations give minerals their distinctive shapes and structures.
Silica appears in various forms, such as fine powder, glass spheres, and crystalline structures. Each form has its practical applications. For instance:

• In the glass industry, silica is a principal ingredient.
• In electronics, silica serves as an insulator or semiconductor.
• It is also used in manufacturing concrete, ceramics, and even as a food additive.

Its pervasive nature and versatile characteristics make silica indispensable in numerous scientific and industrial fields.

Silicon dioxide

Silicon dioxide is the chemical representation of silica. It's a compound consisting of one silicon atom covalently bonded to two oxygen atoms.
The molecular formula for this compound is simple yet powerful: SiO₂. It forms the foundation for many vital materials, specifically quartz and sand.
Silicon dioxide is usually found in a solid state and can create complex structures due to the strong bonds between silicon and oxygen atoms.

• In terms of abundance, silicon dioxide is one of the largest mineral components of the Earth's crust.
• This compound's key role is not only in earth sciences but also in technological fields.

Silicon dioxide's importance can't be overstated; it's a critical part of the digital world as it serves as a critical material in the manufacturing of electronics and semiconductors.

Crystalline structure

The crystalline structure of quartz is what gives this mineral its unique and beautiful properties. In crystallography, this refers to an orderly repeating array of atoms in a solid.
For quartz, these atoms are silicon and oxygen, forming an intricate network. The attractive pattern is due to the way these atoms bond at 109.5° angles within the crystal lattice.
Crystals are characterized by their external geometric shapes and well-defined edges. Quartz, due to its crystalline nature, can form a variety of shapes depending on the conditions of its growth:

• Prismatic crystals
• Hexagonal structures
• Pyramid-like appearances

Beyond aesthetics, the crystalline structure is fundamental in determining the mineral's physical properties, like hardness and fracture patterns, which are critical for various applications in jewelry and technology.

Mineral composition

Mineral composition refers to the elements and compounds that make up a mineral, which directly affects its characteristics and uses. In the case of quartz, its primary composition is silicon and oxygen, forming silicon dioxide.
This specific composition is what makes quartz so ubiquitous across different environments and uses. Its stability and resistance to weathering make it a dominant mineral in the Earth's crust.
Composition can also impact a mineral's:

• Color
• Hardness
• Density
• Reactivity

Quartz, given its specific silica-rich composition, is valued not only for its durability but also for its versatility. It's used extensively from jewelry to technology and industry.