Crystal Structure and Properties

• Crystals are solids with a highly ordered microscopic structure.
• Polycrystals are composed of many microscopic crystals.
• Amorphous solids, like glass, have no periodic arrangement.
• Crystallization is the process of crystal formation.
• Lead crystal and crystal glass are actually types of glass, not crystals.
• Crystals are recognized by their flat faces and sharp angles.
• Euhedral crystals have well-formed flat faces, while anhedral crystals do not.
• Flat faces of a crystal grow larger and smoother over time.
• Crystallographic forms are sets of possible faces related by crystal symmetry.
• A crystal's habit is its visible external shape.
• Crystals have unique physical and chemical properties.
• Some common properties of crystals include transparency, hardness, cleavage, and optical properties.
• Crystals can exhibit various colors due to the presence of impurities or defects in their lattice.
• The arrangement of atoms or molecules in a crystal lattice determines its electrical conductivity.
• Crystals can also exhibit piezoelectric and ferroelectric properties, which make them useful in electronic devices.
• Crystals have a wide range of applications in various industries.
• Gemstones, such as diamonds and rubies, are highly valued for their beauty and rarity.
• Crystals are used in electronics for their electrical and optical properties.
• Some crystals, like quartz, are used in timekeeping devices such as watches and clocks.
• Crystals are also used in scientific research, medicine, and energy storage technologies.

Crystallography and Crystal Systems

• Crystallography is the science of measuring the atomic arrangement of a crystal.
• X-ray diffraction is a widely used crystallography technique.
• Crystallographic databases store large numbers of known crystal structures.
• Crystallography helps understand the properties and behavior of crystals.
• Crystallography has contributed to various fields such as materials science and chemistry.
• Crystals have a repeating pattern of atoms or molecules arranged in a three-dimensional lattice.
• The arrangement of atoms or molecules in a crystal lattice determines its symmetry and crystal system.
• Different crystal systems include cubic, tetragonal, orthorhombic, monoclinic, triclinic, and hexagonal.
• Crystal structures can be described using X-ray crystallography, which reveals the positions of atoms within a crystal lattice.
• Crystallographers use mathematical models and symmetry operations to study and classify crystal structures.

Crystal Formation and Occurrence

• Crystals are formed through a process called nucleation.
• Nucleation occurs when atoms or molecules come together to form a solid structure.
• The arrangement of atoms or molecules in a crystal lattice determines its shape and properties.
• Crystals can form in various environments, including geological, biological, and chemical processes.
• Factors such as temperature, pressure, and chemical composition influence crystal formation.
• Crystals are found in solid bedrock.
• Ice crystals are a natural occurrence.
• Calcite crystals can be found in fossil shells.
• Most inorganic solids are polycrystals.
• Glass is an example of an amorphous solid.

Crystallographic Space Groups and Special Properties

• Crystal structures are characterized by unit cells.
• Unit cells stack to form the crystal.
• There are 219 possible crystal symmetries.
• Crystal symmetries are grouped into 7 crystal systems.
• Each crystal system has specific shapes and arrangements.
• Crystals can have special electrical, optical, and mechanical properties.
• These properties are related to the lack of rotational symmetry in the crystal's atomic arrangement.
• Examples of special properties include the piezoelectric effect and birefringence.
• Electrical conductivity, electrical permittivity, and Young's modulus can vary in different directions in a crystal.
• Glasses or polycrystals can also exhibit these properties if made anisotropic through stress or working.

Crystal Use in Pseudoscientific Practices and Other Concepts

• Crystals are used in crystal therapy.
• They are associated with spellwork in Wiccan beliefs.
• Gemstones are also used in these practices.
• Pseudoscientific beliefs do not have scientific evidence.
• Crystallography is a legitimate scientific study of crystals.
• Crystals range in size from a fraction of a millimeter to several centimeters.
• Exceptionally large crystals can be found, such as the 18m long beryl crystal from Madagascar.
• Crystallization depends on the conditions under which rocks solidify.
• Igneous rocks form from molten magma and can have varying degrees of crystallization.
• Metamorphic rocks like marbles and quartzites undergo recrystallization under high temperature and pressure conditions.
• Water-based ice exists in various forms such as snow, sea ice, and glaciers.
• A snowflake is a single crystal or a collection of crystals.
• Ice crystals can form from cooling liquid water or from supersaturated gaseous solutions.
• Ice expands when it crystallizes, unlike most substances.
• Ice cubes are examples of polycrystals.
• Living organisms can produce crystals like calcite, aragonite, and hydroxylapatite.
• Molluscs produce calcite and aragonite, while bones and teeth contain hydroxylapatite.
• Crystals grown by organisms form from aqueous solutions.
• These crystals play important roles in biological structures and functions.
• Organigenic crystals can have unique properties and structures.
• Polymorphism refers to the ability of a solid to exist in multiple crystal forms.
• Water ice, for example, can exist in hexagonal, cubic, and rhombohedral forms.
• Different polymorphs can have distinct properties and structures.
• Allotropy is the polymorphism observed in pure chemical elements.
• Polymorphism and allotropy contribute to the diverse properties of materials like carbon and steel.
• Crystallization is the formation of a crystalline structure from a fluid or dissolved materials.
• The final form

Crystal Data Sources

Reference	URL
Glossary	https://harryandcojewellery.com.au/blogs/glossary/crystal
Wikipedia	http://en.wikipedia.org/wiki/Crystal
Wikidata	https://www.wikidata.org/wiki/Q43533
Knowledge Graph	https://www.google.com/search?kgmid=/m/01t4h