Question

In which of the following silicates, cyclic structure is present? (a) Emerald (b) Talc (c) Mica (d) Asbestos

Short answer

Emerald (a) has a cyclic structure.

Step-by-step solution

Understand Cyclic Silicates

Cyclic silicates, also known as ring silicates, are characterized by their ring-like structure. The silicate units are linked together in a closed loop or ring shape, typically containing 3, 4, 5, or 6 tetrahedral units.

Analyze Each Option for Structure Type

Examine each of the given options to see if they fit the description of cyclic silicates. - **Emerald (a):** Is a variety of beryl and has a ring silicate structure with 6-membered rings. - **Talc (b):** Is a type of phyllosilicate and forms sheet structures. - **Mica (c):** Is also a phyllosilicate, forming layered structures. - **Asbestos (d):** Usually forms fibrous structures, typically in the format of amphibole minerals, not cyclic.

Identify the Correct Structure Type

From the analysis: - Emerald (a) is the only structure that forms a cyclic silicate with its 6-membered rings of silica. - Talc (b) and Mica (c) are phyllosilicates, and Asbestos (d) is fibrous, none of which are cyclic silicates.

Conclude the Answer

Since Emerald (a) fits the description of a cyclic structure with its 6-membered rings of silicate units, it is the correct choice.

Key concepts

Ring Silicates

Ring silicates, also referred to as cyclic silicates, are unique because they possess a closed-loop or ring structure. These rings usually consist of 3, 4, 5, or 6 tetrahedral units.
The basic building block of these silicates is the silica tetrahedron, composed of one silicon atom bonded to four oxygen atoms.

• In ring silicates, each silica tetrahedron shares two of its oxygen atoms with neighboring tetrahedra, forming the ring structure.
• These shared oxygen atoms create a balance in the charge, making the structure more stable.
• The most commonly found ring silicates contain 6-membered rings, as seen in minerals like beryl and emerald.

Ring silicates are important in mineralogy for understanding the structural diversity among silicate minerals.

Silicate Structure Types

Silicate minerals are the most abundant group of minerals on Earth, thanks to the versatile silicon-oxygen tetrahedron. This structure can connect in various ways, leading to different types of silicate structures.
There are several major types based on how the tetrahedra are arranged and linked:

• Nesosilicates: Isolated tetrahedra linked only by ionic bonds with metal ions.
• Sorosilicates: Double tetrahedral groups formed by sharing one oxygen atom.
• Cyclic Silicates (Ring Silicates): Tetrahedra forming closed rings by sharing two oxygens per tetrahedron.
• Inosilicates: Single or double chains of tetrahedra.
• Phyllosilicates: Tetrahedra arranged in sheets by sharing three oxygens.
• Tectosilicates: A three-dimensional framework of tetrahedra sharing all four oxygens.

Each type of arrangement gives the minerals in that group distinctive physical properties and stability.

Phyllosilicates

Phyllosilicates, also known as sheet silicates, are defined by their structure of sheets formed by silica tetrahedra. In this structure:

• Each silica tetrahedron shares three of its oxygen atoms with neighboring tetrahedra, creating extensive two-dimensional sheets.
• This arrangement results in a high surface area, which influences the mineral's properties, such as elasticity and flexibility.
• Common minerals in this group include mica, talc, and chlorite.

Phyllosilicates are known for their perfect cleavage in one direction, making them easy to split into thin sheets. This property is useful in a range of industrial applications, from cosmetics to electrical insulators.

Mineralogy

Mineralogy is the branch of geology concerned with the study and analysis of minerals. This science explores:

• The formation, composition, and properties of minerals.
• Minerals' roles and applications in various industries.
• Identification and classification of minerals based on their chemical composition and crystalline structure.

Understanding mineralogy is essential for disciplines like mining, gemology, and environmental science.
Silicate minerals, including ring silicates and phyllosilicates, are a significant focus within mineralogy due to their prevalence and economic importance. From jewelry making to technological applications, mineralogy helps us unravel the complex nature of Earth's building blocks.