test 1 Flashcards
(38 cards)
What symmetry operation is found in all minerals?
Translations are found in all minerals, where crystal structures are repeated at fixed distances without rotation or inversion.
What symmetry operations are used to divide minerals into 32 crystal classes?
The symmetry operations include:
* Mirror planes (m)
* Rotation Axes (A1, A2, A3, A4, A6)
* Point of symmetry (i)
* Inversion (i)
* Rotoinversions
What is the role of mirror planes in crystal symmetry?
Mirror planes are reflections along a plane, cutting the object into equal halves.
How do rotation axes function in crystal symmetry?
Rotation axes allow for a rotation of 360, 180, 120, 90, or 60 degrees around a rotational axis without changing the arrangement of motifs.
What is glide reflection in the context of symmetry operations?
Glide reflection involves a reflection combined with a translation by ½ the repeat distance.
What defines the cubic/isometric crystal system?
In the cubic/isometric system, a = b = c and all angles are 90 degrees.
What is the axial arrangement in the tetragonal crystal system?
In the tetragonal system, a = b ≠ c and all angles are 90 degrees.
What is the definition of Miller indices?
Miller indices (hkl) are assigned by identifying where a crystal face intersects the crystallographic axes, measuring intercepts, and finding the lowest whole numbers.
What is a Wulff Net used for?
A Wulff Net is used to plot mineral faces and symmetry operations.
How are minerals classified based on chemical composition?
Minerals are classified into:
* Native elements
* ‘Ides’ (simple anions)
* ‘Ates’ (anion complexes)
What types of chemical bonds are found in minerals?
The four types of chemical bonds in minerals are:
* Ionic
* Covalent
* Metallic
* Van Der Waals
What is the difference between hardness and tenacity?
Hardness is a mineral’s resistance to being scratched; tenacity is the resistance to breaking.
What is the definition of a mineral?
A mineral is a naturally occurring, homogeneous solid with a definite chemical composition and an internal repeating structure.
What is an example of a mineral that is not classified due to its structure?
Amorphous solids like glass and amber are not classified as minerals.
What is the significance of color in mineral identification?
Color is a good identifying characteristic if it has a strongly colored major component; it is not reliable when it arises from trace constituents.
What does the term ‘Euhedral’ refer to in mineralogy?
Euhedral refers to minerals with complete or nearly complete faces.
What is a pseudomorph?
A pseudomorph is a mineral with an outward crystal form inherited from an earlier mineral.
What is the difference between anion complexes and simple anions?
Anion complexes contain complex anion groups surrounding a central atom, while simple anions consist of a single negatively charged anion.
What is the difference between density and specific gravity?
Density is mass divided by volume; specific gravity is the ratio of a substance’s mass to the mass of an equal volume of water.
What is the role of Bravais lattices in crystallography?
Bravais lattices represent the repeating patterns of atoms in a crystal structure, defining spatial arrangements.
What does the term ‘acicular’ describe in mineralogy?
Acicular describes a crystal habit where minerals form long, slender, needle-like crystals.
What is the significance of Moh’s Hardness scale?
Moh’s Hardness scale ranks minerals from softest (talc) to hardest (diamond) based on their resistance to scratching.
What defines a mineral as an anhedral?
An anhedral mineral is one that has no visible clear faces.
What is the difference between ‘twinning’ and ‘polysynthetic twin’?
‘Twinning’ refers to a mineral lattice disruption allowing a second lattice formation; ‘polysynthetic twin’ involves multiple parallel twins.
