seeds of growth (exer #5)

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crystalline solid

geometric solids with a systematic, internal arrangement of ions or molecules that have bonded together;

this is defined base on its internal structure rather than its external appearance;

• ex. minerals

unit cell

term for the simplest repeating design for a crystalline solid, which is repeated through the 3-dimensional structure of the crystals

True

TRUE OR FALSE:

Because of the internal cubic pattern of NaCl, the typical shape of halite crystals is also cubic.

solutions, melts, vapors

MECHANISMS OF CRYSTALLIZATION:

Crystals may form from ______, ______, ______

nucleation, growth, diffusion

3 processes which are involved in the formation of crystals

1. initiates the formation of a stable crystal seed

2. expands that seed into a larger crystal

3. transports the building blocks (atoms, ions, or molecules) to the reaction sites

nucleation

3 PROCESSES IN FORMATION OF CRYSTALS:

this begins when ions or molecules become concentrated in a specific area of the medium;

• these clusters of ions must reach a critical size, otherwise, they may just spontaneously separate.

critical size, protocrystal

UNDER NUCLEATION:

These clusters of ions must reach a _____ _____, otherwise, they may just spontaneously separate

• when the critical size has been attained, the attraction between molecules becomes strong enough for them to bond together and form a ________.

protocrystal

UNDER NUCLEATION:

When the critical size has been attained in nucleation, the attraction between molecules becomes strong enough for them to bond together and form a _______;

this ______ develops into a stable nucleation site to which more molecules adhere themselves.

True

TRUE OR FALSE:

Growth continues as more components bond to the crystal.

Eventually, the crystal precipitates out of the medium, and reaches equilibrium with the components still dispersed in the medium.

equilibrium, diffusion

UNDER NUCLEATION:

at ______, the crystal stops increasing in size;

both nucleation and growth rely on the _______ or movement of chemical components throughout the medium and onto the crystal surface.

nucleation rate

UNDER NUCLEATION:
defined as the number of new seed crystals that develop per volume per time unit

growth rate

UNDER NUCLEATION:

increase in crystal radius over time

high, low

NUCLEATION RATES:

1. fine-grained rocks (aphanitic) - ____; lots of nucleus, not concentrated

2. coarse-grained rocks (phaneritic) - ____; small amounts of nucleus

faster, slower

GROWTH RATES:

1. fine-grained rocks (aphanitic) - forms minerals ____ due to rapid cooling

2. coarse-grained rocks (phaneritic) - ____ due to being underground (hot)

crystallization from solution

3 MECHANISMS OF CRYSTALLIZATIONS:

in _____, the components of the crystal (solute) are separated into individual units in the solvent;

• by removing this solvent through evaporation, the ions and molecules fall naturally into their appropriate place in the repetitive structure.

• ex. formation of rock salt from seawater

False; should be may form

TRUE OR FALSE:

Crystals cannot form from solutions by lowering temperature or pressure.

• For example, more salt can be dissolved in hot water than in cold water, so the solution becomes saturated with respect to salt in higher temperatures.

crystallization from melts

3 MECHANISMS OF CRYSTALLIZATION:

Crystals form from _____—the liquid portion of magma—similarly from solutions, except that instead of solutes simply separating from solvents, _____ involve a change of phase.

• formation of ice from water,

formation of igneous rocks from magmas

UNDER MELTS:

Magmas contain a random distribution of ions of many elements. This variety makes it possible for different minerals to form, but not at the same time, because of differences in temperatures.

• With a decrease in temperature, these ions become attracted to one another, forming the crystal nuclei of these minerals.

• As crystal growth proceeds, these nuclei enlarge to become the mineral grains of the resulting igneous rock.

crystallization from vapors

3 MECHANISMS OF CRYSTALLIZATION:

When the _____ are cooled, the ions or molecules dispersed in the _____ are brought in proximity to each other and allowed to bond, producing a crystalline solid.

• when a substance transitions directly from a gas or vapor state into a solid crystal lattice

• ex. formation of snowflakes from air that is heavy with water vapor at or below the freezing temperature of water.

fumeroles

UNDER CRYSTALLIZATION FROM VAPORS:

An example of this process is the formation of sulfur around the mouths of volcanic vents, called _____, which emit gases that contain SO₂, HCl, CO₂, H₂O, H₂S, and elemental sulfur.

• at certain temperatures, reactions among these gases result in formation of native sulfur

habit

CRYSTAL SHAPE & FACES:

refers to the physical shape of a crystal;

controlled by the environment in which the crystal formed;

crystals exhibit numerous kinds of _____, some of which mirror their systematic atomic structure

True

TRUE OR FALSE:

The more complex the internal structure, the more intricate its external shape or habit.

crystal faces

CRYSTAL SHAPE & FACES:

refer to the individual, smooth planes on a crystal;

development of these is dependent on conditions during crystallization

• euhedral, subhedral, anhedral

True

TRUE OR FALSE:

Since the development of faces (i.e. how sharp or irregular the edges are) is dependent on the conditions during crystallization, thus, it can be expected that not all crystals will have perfectly developed faces.

The Law of Constancy of Interfacial Angles

states that “The angles between equivalent faces of crystals of the same substance, measured at the same temperature, are constant.” (Nicolaus Steno, 1669)

False; always be equal

TRUE OR FALSE:

According to Steno’s Law, if a single mineral species occurs in different sizes and shapes, the angle between pairs of corresponding faces will not be equal when measured at the same temperature.

euhedral

TYPES OF CRYSTAL FACES:

type of crystal when it exhibits well-formed faces

subhedral

TYPES OF CRYSTAL FACES:

type of crystal when its faces are imperfect

anhedral

TYPES OF CRYSTAL FACES:

type of crystal when no faces develop

inversely proportional

RELATIONSHIPS BETWEEN VARIABLES:

temperature during crystallization & rate of crystallization

proportional

RELATIONSHIPS BETWEEN VARIABLES:

temperature during crystallization & crystal size

inversely proportional

RELATIONSHIPS BETWEEN VARIABLES:

rate of crystallization & crystal size

proportional

RELATIONSHIPS BETWEEN VARIABLES:

rate of crystallization & crystal abundance