Lecture notes, Mineralogy
Chapter 1 and 2
I. Crystal Form and habit.
a. Form is the true shape of a crystal, usually described in geometric terms.
b. Habit is the outward appearance of a crystal, regular or irregular.
c. Euhedral – perfect crystal. Good on all sides
i. Prismatic
ii. Rhombohedral
iii. Cubic
iv. Octahedral
v. Pinacoidal – with the pronounced development of one or more two-sided forms
d. Subhedral, less than perfect but the general crystal form can be seen.
e. Anhedral – shows no crystal form
II. Intergrowths, twins and striations
a. Parallel growths – where the crystallographic axes and faces are parallel
b. Twins – symmetrical intergrowth of two or more crystals of the same substance.
i. Contact twins – share wall or plane
ii. Penetration twins share space
iii. Polysynthetic twinning –
III. State of Aggregation
a. Types of habits, see page 22
IV. Luster, Color, and Streak
V. Other Properties
a. Transparent, translucent, opaque
b. Opalescence, iridescence ( or schiller and labradorescence),
c. Chatoyancy and Asterism
i. Such as in Tiger Eye, multiples are asterism
d. Luminescence – glow in the dark
e. Fluorescence and Phosphorescence, with uv radiation. If it continues after the light has been turned off, then it is phosphorescent.
VI. Cleavage, parting and fracture
a. Cleavage is the tendency of a mineral to break parallel to atomic planes
i. Describe quality, good poor ect.
ii. Use geometric names or miller index to describe shape.
b. Parting – break along planes of structural weakness, by pressure or twinning or exsolution
c. Fracture – Conchoidal, fibrous and splintery, Hackly or jagged, uneven or irregular.
VII. Hardness – Mohs Hardness scale. Know on page 31
a. Use fresh surface
b. Scratches cannot be rubbed off.
c. Imperfect minerals will have imperfect reading
d. Vectorial property
e. Link between hardness and chemical composition
i. Hydrous are soft <5
ii. Halides carbonates sulfates and phosphates are soft <5.5
iii. Sulfides are soft except pyrite
iv. Anhydrous oxides and silicates are hard >5
VIII. Tenacity
a. Brittle (ionic is more brittle)
b. Malleable
c. Sectile – can be cut with a knife
d. Ductile – made into wire
e. Flexible – can bend but not spring back
f. Elastic –
IX. Specific Gravity
a. Usually listed as an average
b. Heavy liquids
X. Magnetism
XI. Radioactivity
XII. Solubility in HCL
XIII. Piezoelectricity
a. Related to chemical bonding
i. Metals are conductors
ii. Sulfides are semiconductors
iii. Covalent bonds and ionic bonds are non conductive
iv. Use of quartz in radios and watches. Quartz mechanically deformed an vibrates with an alternating current
v.