18 Questions
What is the characteristic feature of a tetragonal crystal structure?
Two axes are of equal length and the third axis is different, all intersecting at 90° angles.
Which of the following is a characteristic of a hexagonal crystal structure?
Three symmetrical axes of equal length in the same plane, with a fourth axis intersecting at 90°.
What is the characteristic of an orthorhombic crystal structure?
Three axes of different lengths intersecting at 90° angles.
Which of the following is a characteristic of a monoclinic crystal structure?
Three axes of unequal length, with two axes in the same plane at right angles and the third axis inclined.
What is the characteristic of a triclinic crystal structure?
Three axes of different lengths intersecting at angles other than 90°.
Which of the following is a characteristic of pyrite's tetragonal crystal structure?
Two axes of equal length and one axis of different length, all intersecting at 90° angles.
What is the characteristic that describes the external expression of the internally ordered arrangement of atoms?
Crystal Form
Which crystal structure has three axes at 90° angles and all the same length?
Orthorhombic
Which crystal structure is characterized by unequal axes intersecting at oblique angles?
Triclinic
What property of minerals refers to their resistance to scratching and is typically measured on the Mohs scale?
Hardness
Which crystal structure has a base with six sides and an axis of symmetry passing through its center?
Hexagonal
What crystal structure is distinguished by having two axes at 90° angles and one oblique axis?
Monoclinic
What property of a mineral refers to the weight or heaviness of the mineral?
Specific Gravity
Which type of crystal structure consists of four oxygen atoms surrounding a silicon atom?
Monoclinic Crystal Structure
What classification category includes minerals that contain iron or magnesium joined to the silicate structure?
Silicates
Which property of a mineral refers to its resistance to scratching?
Hardness
Which crystal structure category includes minerals with unequal axes at oblique angles?
Triclinic Crystal Structure
Which crystal structure category includes minerals with three mutually perpendicular axes of different lengths?
Orthorhombic Crystal Structure
Study Notes
Crystal Structures
- Tetragonal crystals have three axes, two of equal length, and one different, with all axes perpendicular to each other.
- Orthorhombic crystals have three axes of different lengths, intersecting at 90° angles.
- Hexagonal crystals have three symmetrical axes of equal length, and a fourth axis that may be longer or shorter, intersecting at 90° angles.
- Monoclinic crystals have three axes of unequal length, with two axes in the same plane at right angles to each other, and the third axis inclined.
- Triclinic crystals have three axes of different lengths, intersecting at angles other than 90°.
Mineral Properties
- Crystal form is the external expression of the internally ordered arrangement of atoms.
- There are 6 major crystal forms: Isometric, Tetragonal, Orthorhombic, Hexagonal, Monoclinic, and Triclinic.
- Isometric crystals have three axes of equal length, at 90° angles to each other.
- Hardness is a measure of a mineral's resistance to scratching.
- Luster is the way a mineral reflects light.
- Color is a mineral's characteristic color.
- Streak is the color of a mineral's powder.
- Cleavage is the tendency of a mineral to break along flat planes.
- Specific gravity is the ratio of a mineral's weight to the weight of an equal volume of water.
Mineral Classification
- Minerals can be classified into 7 major groups: Silicates, Native Elements, Halides, Carbonates, Oxides, Sulfates, and Sulfides.
- Silicates are composed of silicon-oxygen tetrahedrons, and can be divided into ferromagnesian and non-ferromagnesian silicates.
Other Key Facts
- Minerals have invariant compositions and distinctive properties.
- Minerals are naturally occurring, inorganic, and homogeneous solids.
- Minerals have a definite chemical composition and ordered internal structure.
- Ore minerals are minerals that contain a high concentration of a valuable element or compound.
Explore the differences in crystal structures between tetragonal and orthorhombic systems. Learn about the axes length relationship and angles in pyrite and zircon crystals. Understand how the arrangement of axes impacts the overall shape of the crystals.
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