Mineral Properties & Crystal Systems

The correct answer is Isometric. Isometric crystal systems have three equal axes that intersect at 90 degrees. This means that all sides of the crystal are equal in length and all angles between the faces are 90 degrees. This crystal system is characterized by its symmetry and regularity in shape.

Fracture refers to the breakage of a mineral in a direction other than cleavage or parting. It occurs when a mineral does not have a specific pattern of atomic arrangement that allows it to break along planes of weakness. Unlike cleavage, which produces smooth and flat surfaces, fractures result in irregular and rough surfaces. This term is commonly used in mineralogy to describe the physical properties of minerals and their ability to break under stress.

Triclinic is the correct answer because in this crystal system, all three axes are not perpendicular to each other, and the angles between them are all unequal. This means that the crystal structure has no symmetry and is the least symmetrical of all the crystal systems.

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Crystal habit refers to the general outward appearance or shape of a crystal. It describes the way a crystal grows and the arrangement of its faces. Different minerals have different crystal habits, which can be used to identify them. For example, some minerals may have a cubic habit, meaning they form cubes, while others may have a prismatic habit, forming long, slender crystals. Understanding crystal habit is important in mineralogy and can provide valuable information about the conditions in which a crystal formed.

Cleavage refers to the tendency of a mineral to break along preferred atomic planes. This means that when a mineral is subjected to external forces, it will break along specific planes of weakness within its atomic structure. Cleavage can result in smooth, flat surfaces or planes in the mineral, creating distinct crystal faces. This property is often used to identify minerals, as different minerals have different cleavage patterns.

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Anhedral is the correct answer because it refers to the absence or very few crystal faces in a mineral specimen. This means that the mineral does not exhibit well-formed crystal faces and instead appears irregular or shapeless.

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The correct answer is Hexagonal. Hexagonal crystal systems have angles of 90 degrees and 120/60 degrees. This means that the angles between the crystal faces in a hexagonal crystal are either right angles or angles of 120 or 60 degrees.

Subhedral is the correct answer because it refers to a crystal that has some well-formed faces, but is not completely bounded by them. It is a term used to describe crystals that have both crystal faces and irregular surfaces. This means that while there are some distinct faces present, they are not fully developed and the crystal as a whole does not have a well-defined shape.

The given answer, "Hexagonal," is the correct answer because the statement "c>a1=a2=a3" indicates that the crystal system being described has a greater c-axis length compared to the lengths of its a-axis and b-axis, which are equal. This characteristic is specific to the hexagonal crystal system, where the c-axis is perpendicular to a plane of symmetry and the a-axis and b-axis are of equal length and intersect at 120-degree angles.

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Euhedral refers to a crystal that has well-formed, distinct faces. In other words, the crystal has a regular and symmetrical shape with clearly defined surfaces. This term is used to describe crystals that have grown in an environment with minimal interference or obstruction, allowing them to develop their characteristic shape. The other options, such as anhedral and subhedral, refer to crystals that have irregular or partially formed faces, while cleavage and fracture describe the ways in which crystals break.

The given description states that crystal systems c and b are at 90 degrees, and the a-axis is inclined downward to the front. This arrangement corresponds to the monoclinic crystal system. In the monoclinic system, the three axes have different lengths, and only one axis is perpendicular to the other two. The other two axes are not perpendicular to each other, which is consistent with the given description. Therefore, the correct answer is Monoclinic.

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Tetragonal crystal systems have one axis that is longer or shorter than the other two, but all three axes are perpendicular to each other. In this case, the given statement "c > a = b" suggests that the length of the c-axis is greater than the length of both a and b axes, but the lengths of a and b axes are equal. This matches the characteristics of a tetragonal crystal system, making it the correct answer.

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The given answer, "tetragonal system," is the correct answer for the question. However, without any context or details provided in the question, it is not possible to provide a specific explanation for why this answer is correct. The tetragonal system is one of the seven crystal systems in crystallography, characterized by three axes of different lengths, two of which are perpendicular to each other, and the third axis is perpendicular to the other two. It is often found in minerals such as zircon and staurolite.

A triclinic system refers to a crystal system in which the crystal lattice has no symmetry. It is the least symmetric among all the crystal systems, with the unit cell having three unequal axes and the angles between them being different from 90 degrees. This lack of symmetry allows for the maximum number of possible crystal forms. In a triclinic system, the crystallographic axes can have any length and can be inclined at any angle to each other. This results in a unique arrangement of atoms within the crystal lattice, giving rise to distinct physical and optical properties.

The given answer, "monoclinic system," is the correct answer. The monoclinic system is one of the seven crystal systems in which crystals are classified based on their symmetry and lattice structures. In the monoclinic system, the crystal has three unequal axes, with one axis perpendicular to the other two, which are inclined to each other at an angle other than 90 degrees. This system is characterized by a unique symmetry and lattice arrangement, making it distinct from other crystal systems such as cubic, tetragonal, or orthorhombic.

The given correct answer, "orthorhombic system," refers to a crystal system in which the crystal lattice has three mutually perpendicular axes of different lengths. The angles between these axes are all 90 degrees. In an orthorhombic system, the crystal structure exhibits threefold symmetry and lacks a center of symmetry. This system is one of the seven crystal systems commonly found in nature and is characterized by its unique symmetry and lattice parameters.

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Crystal systems are classified based on the symmetry of their unit cells, the smallest repeating unit in a crystal lattice. The systems with all axis angles equal to 90 degrees (meaning they are perpendicular to each other) are:

Isometric: All axes are of equal length. Examples include cubic crystals like diamond and garnet.

Tetragonal: Two axes are of equal length, and the third is different. Examples include zircon and rutile.

Orthorhombic: All three axes are of different lengths. Examples include topaz and olivine.

Triclinic is one of the seven crystal systems. In triclinic crystals, the lattice parameters are all different and the angles between them are all unequal. This results in a non-symmetrical crystal structure. Triclinic crystals have the lowest degree of symmetry among all crystal systems.

The given crystal systems are listed in a specific order: Hexagonal, Isometric, Monoclinic, Orthorhombic, Tetragonal, and Triclinic. The correct answer, Monoclinic and Orthorhombic, indicates that these two crystal systems come after each other in the given order. Therefore, Monoclinic is the crystal system that appears immediately before Orthorhombic.