Skeleton of crystals

Crystallography is the science of crystals the word crystals is of Greek origin "Congealed by cold". Crystals is a homogeneous solid bounded by naturally formed plane faces which can be related to regular internal arrangements not atoms (Klein's and Hurbut 1985) Minerals are crystalline. Which means minerals might be a Crystal forms.



Four Aspect of Crystallography
1. The character of minerals in general

2. The internal or atomic structure

3. The various forms of crystals and their division into classes and systems

4. Methods of studying crystals



Crystallization and Crystal Growths
Crystallization is the formation of Crystals. A formation of crystalline substance.

1. A change from the liquid to solid phase

2. A change from the gaseous phase to the solid

3. A change from one solid phase to another, accompanied by alterations of the shape of the crystals structure.

Note: The first is crystallization from a melt or solution second is crystallization by sublimation. And the third is recrystallization.




History of Crystals Forms 
Philip (1971) defined a form as the assemblage of faces necessitated by the symmetry when one facesbus given, Klien and Hurbut (1985) wrote that a form consisted of group of crystals faces, all of which have the same relationship to the elements of symmetry and is displayed the same Chemical and physical properties because all are underlained by the atoms in the same geometrical arrangements.



Crystals with similar faces are simple forms e.g magnetite and sphalerite crystalline in octahedral form. Forms facesbbut because the faces are similar they constitutes a form.



Crystals Habits.
The habit of a Crystal is the general aspects conferred by the relative development of the different forms. The term "Habits' is used to denote the general shapes of Crystals such as cubic, octahedral prisometer.




It includes the shape and irregularities of crystals growth, e.g Quartz crystsalline in hexagonal form and had horizontal stations.



It is the common or combination of forms in which minerals crystallize.

Zones. Many crystals faces are arranged in zomes. A zone is a complement of faces intersecting along parallel .


Prism 
Is a name given to a form whose faces are parallel to the veritical c -axis and cut the other two axes. The prism is an open form composed of 3,4,6,8 or 12 faces all which are parallel to the same axis.



Pyramid
An open form composed of 3,4,6,8, or 12 non- parallel faces that meet at a point. In a pyramid alaal the axis are cut by the faces. All the axes are oriented in the same axis.



Internal Orders in Crystals And Crystals Morphology.
In the crystal the small dots represent Na atom where as the little circle stand for Cl. At each point (Motif) The surrounding is uniform. Each Na and Cl atom is surrounded by Cl atoms and 6 Na atomes.


The ordered arrangements is stable just as a brick wall constructed with carefully positioned blocks in an ordered arrangements, provides aore stable and less energetic configuration than a brick wall made with a random arrangements of similar bricks the bricks in these walls can be considered as the Motif.



Bragg's Equation And Indentification of a Crystals
Sir W.H Bragg observed that there might be a way of using X-rays to study crystals Because the wavelength of X-rays and distance between atomes in a Crystals are the same. Hence he combine the findings of Roentgen's and laue into a useful theory to study the structure of crystals.




He reduce his mathematical sequence into an equation wavelength..
The interfacial angles is the important and is the angle between any two faces of s crystals. It's the angle between two normal to the two faces or planes in the diagram below is the interfacial angle where as A is the plane angle between F and F1.