Yasmin Azeem

8/8/2019 Yasmin Azeem

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Yasmin Azeem


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Quartz Crystals

Sulfur


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What is a mineral?

Naturally occurring

Non-organic Characteristic chemical composition

Distinctive physical properties

Crystalline structure


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Mineral A mineral is any naturally-

occurring, homogeneoussolid that has a definite

ch

emical composition anda distinctive internal crystal

structure.


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Most minerals arechemical compounds, a

small number (e.g.,sulfur, copper, gold) are

elements.


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Minerals combine with each

other to form rocks. For example,granite consists of the minerals

feldspar, quartz, mica, and

amphibole in varying ratios.

Rocks are thus distinguished from

minerals by their heterogeneouscomposition.


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Minerals differ from one

another because eachhasa specific chemical

composition and a uniquethree-dimensional

arrangement of atomswithin its structure.


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These differences result in a

variety ofphysical properties,

including the minerals'

appearance, how they break,how well they resist being

scratch

ed, evenh

ow th

eysmell, taste, and feel.


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Mineral properties

Color

Luster

Habit (Shape)

Cleavage & Fracture

Streak

Hardness

Other


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Color Color results from a

minerals chemicalcomposition, impurities

th

at may be present, andflaws or damage in the

internal stru

ctu

re.


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The Many Colors of Fluorite


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Luster The luster of a mineral is the way its

surface reflects light. Most terms

used to describe luster are self-explanatory: metallic, earthy, waxy,

greasy, vitreous (glassy), adamantine

(or brilliant, as in a faceted

diamond).


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Non-metallicMetallic


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Streak The color of a mineral when it is

powdered is called the streak of the

mineral. Streak can be determinedfor any mineral by rubbing the

mineral across the surface of a hard,

unglazed porcelain material called a

streak plate.


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Streak Color for a Few

Common MineralsBlack - GraphiteBlack - Pryite

Black - MagnetiteBlack - ChalcopyriteGray - Galena

Limonite - Yellow-brownHematite - Red-brown


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Streak:

The powdered form of a mineral


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Cleavage & Fracture

Cleavage: planes of weaknessalong whichminerals can break

Fracture: surfaces along whichminerals can break


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Cleavage & Fracture

Best identified on a fracture surface


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Cleavage of

Calcite


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Examples of Cleavage


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Fracture When bonds between atoms are

approximately the same in all

directions within a mineral, breakage

occurs either on irregular surfaces

(splintery or irregular fracture) or

along smooth, curved surfaces

(conchoidal fracture), similar to

those formed when thick pieces of

glass are broken.


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Hardness The hardness of any object

is controlled by th

estrength of bonds between

atoms and is measu

red bythe ease or difficulty with

wh

ich

it can be scratch

ed.


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Diamond is the hardest

mineral, because it can

scratch all others. Talc is

one of the softest; nearly

every other mineral can

scratch it.

iamond is the hardest naturally occurring substance known; it is also


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Hardness:

Based on Mohs scale ofhardness


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Crystal Shape The crystal form for a given

mineral is governed by th

emineral's internal

stru

ctu

re, and may bedistinctive enough to help

identify the mineral.


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Mineral Habit (Shape)

Shape a mineral

takes if grown

unimpeded


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Quartz forms elongated,

six-sided prisms capped

with pyramid-like faces;

galena and halite occur as

cubes; and garnets develop

12- or 24-sided

equidimensional forms.


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Other PropertiesMagnetism - A few

minerals are attracted to amagnet or are themselves

capable of acting asmagnets


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Feel - Some minerals,

notably talc and

graph

ite, feel greasyor slippery when you

rub your fingers overthem


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Taste - Geologists use as many senses as

possible in describing and identifyingminerals. Taste is one of the last tests to

be conducted, because some minerals

are poisonous. Some minerals taste salty-most notably halite (salt). Sylvite, a

mineral similar in all other properties to

halite, tastes bitter. NEVER TASTE AMINERAL UNLESS INSTRUCTED TO!


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Reaction with Dilute

Hydrochloric Acid-Th

is isactually a chemical property

rather than a physical attribute of

a mineral. Minerals containingthe carbonate anion (C03)

2-

effervesce ("fizz") wh

en a drop ofdilute hydrochloric acid is placed

on them.


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Yasmin Azeem