1. Crystal habits of some common
minerals
• The crystal habit of a mineral describes its visible external
shape. It can apply to an individual crystal or an assembly of
crystals
• .

2. pyrite

3. Twelve-sided garnet crystals

4. • Cleavage or fracture: conchodial fracture
• Hardness: 7
• Color: Red, green, brown
• Other diagnostic: equant 12 sided crystals
• Ca, Fe, Mg, Al, Cr, Mn, silicate

5. Slender tourmaline crystals

6. Prismatic quartz crystals

7. • Cleavage or fracture: conchoidal fracture
• Hardness: 7
• Color: pink, colorless
• Diagnostic properties: elongate six sided
crystals

8. Potassic feldspar

9. CaAlSi2O8 + NaAlSi2O8
• Cleavage and fracture : two directions at 90o
• Hardness: 6
• Other diagnositic: Striations (fine lines) on one
of the two cleavage directions ; solid solution
between sodium (albite) and calcium
(anthornite) plagioclase

10. • cubic (or isometric) crystal system is a crystal
system where the unit cell is in the shape of a
cube. This is one of the most common and
simplest shapes found in crystals and
minerals.

11. • There are three main varieties of these
crystals:
• Primitive cubic (abbreviated cP[1] and
alternatively called simple cubic)
• Body-centered cubic (abbreviated cI[1] or bcc),
• Face-centered cubic (abbreviated cF[1] or fcc,
and alternatively called cubic close-packed or
ccp)

12. • Each is subdivided into other variants listed
below. Note that although the unit cell in
these crystals is conventionally taken to be a
cube, the primitive unit cell often is not. This is
related to the fact that in most cubic crystal
systems, there is more than one atom per
cubic unit cell

13. three crystals of pyrite (FeS2)

14. • A rock containing three crystals of pyrite
(FeS2). The crystal structure of pyrite is
primitive cubic, and this is reflected in the
cubic symmetry of its natural crystal facets.

15. reflected in the cubic symmetry of its
natural crystal facets.

16. The three Bravais lattices which form
cubic crystal systems are:
Pearson symbol: cP
• .

17. primitive cubic system (cP)
• The primitive cubic system (cP) consists of one
lattice point on each corner of the cube. Each
atom at a lattice point is then shared equally
between eight adjacent cubes, and the unit
cell therefore contains in total one atom
(1⁄8 × 8).

18. Body-centered cubic

19. A caesium chloride unit cell
• Each of the two atom types forms a separate
primitive cubic lattice, with an atom of one
type at the center of each cube of the other
type. Altogether, the arrangement of atoms is
the same as body-centered cubic

20. • The body-centered cubic system (cI) has one
lattice point in the center of the unit cell in
addition to the eight corner points. It has a
net total of 2 lattice points per unit cell (1⁄8 × 8
+ 1).

21. function of ionic radius
• more likely to be formed from two elements
whose ions are of roughly the same size (for
example, ionic radius of Cs+ = 167 pm, and Cl−
= 181 pm) .

22. or "221
• The space group of this structure is called
Pm3m (in Hermann–Mauguin notation), or
"221

23. 0,0,x > y,0,0 > 0,z,0
The ℓ, m, and n directional indices are
separated by 90°,

24. Planes and direction