Blogs

By the expression “crystal form” is meant the assemblage of all similar faces which are possible with a certain degree of symmetry. In fig. 9 is represented a crystal form known as a pyramid. In the particular symmetry class to which it belongs the three crystal axes are axes of binary symmetry and the axial planes are lanes of symmetry. Under these conditions, if we assume the presence of the face. A we must have the other seven faces also in order to satisfy the demands of the symmetry.

It is to be noted that in general the Mathematical Ratio of the intercepts of a crystal face upon the crystallographic axes can be expressed by whole numbers or definite fractions. These numbers, or fractions, are commonly simple, such as 1, 2, 3, ½, 1/3, 2/8, etc., and in the great majority of cases are 1 or ∞. This law, that the axial intercepts of all crystal faces form a definite mathematical ratio, is an extremely important one. It is a necessary corollary to the theoretical considerations given on page 8 and following.

Crystal faces are described according to their relations to the crystallographic axes. A series of numbers which indicate the relative distances by which a face intersects the different axes are called its parameters. A face which cuts all three axes at distances from the point of their intersection which are relatively the same as the unit lengths of the axes is said to have the following parameters: 1a, 1b, 1c (see Fig. 9).

Basic Crystallography and Crystallographic Axes. Crystallographic axes are imaginary lines or directions within a crystal to which the crystal face are referred and in terms of which they are described. In the different systems the axes vary in number (three of four), in their relative lengths and in the angles of inclination to each other. As a general case we will consider the crystallographic axes of the Orthorombic System. They are three in number, at right angles to each other, and each has a characteristic relative length.

Symmetry of crystal Plane. A symmetry plane is an imaginary plane which divides a crystal into halves, each of which is the mirror image of the other. Figure 5 will illustrate the character of such a plane. The shaded portion of the figure shows the position of the one plane of symmetry that a crystal of this sort possesses. For each face, edge or point on one side of the plane there is a corresponding face, edge or point in a similar position on the other side of the plane.

And important part of the study of crystallography consists in the measuring and classifying of the interfacial angles on the crystals of all minerals. These measurements are accomplished by means of instruments know as goniometry. For accurate work, particularly in the case of small crystals, a type of instrument known as a reflection goniometry is used. This is an instrument upon which the crystal to be measured is mounted so as to reflect beams of light from its faces through a telescope to the eye.

Law of the Constancy of Crystal Angles. Since the internal structure of any mineral is always constant, and since the possible crystal faces of that mineral have a definite relationship to that structure, it follows that mineral have a definite relationship to that structure, it follows that the faces must have also a definite relationship to each other. This fact may be stated as follows: The angles between two similar faces on the same substance are always the same.

Dry washers have been discredited; criticized and distorted far too many times that it is difficult to get at the truth. To a certain extent in all honesty, only large scale mining operations which use sophisticated equipment are flourishing in recovering fine gold by dry methods in amounts which are large enough to make it cost-effective. On the other hand, there are a very large amount of individual prospectors who make use of the small kind of dry washer. These are with no trouble transportable and are either hand-operated or drive by a little motor.

You need knowing what is an amalgamation process if the gold concentrates that you have carry a very large amount of extremely fine flour gold with mercury in them making it difficult for you to separate them, or if the case is that you just don’t have the time to be bothered in using the blowing box, you may perhaps find it a lot quicker to amalgamate the gold with mercury. You can, after doing the process, retort the mercury off, this will leave you with a 'button' of amalgam.

The blowing box is a one-dimensional box made of heavy copper or tin. Its length is of about eight inches long; its width is of four inches wide at one end and two inches wide at the other end. The long end and sides are at right angles to the bottom and its height is of about one inch high. Make sure to leave the narrow end open. You must place an amount of the fines in the box, hold it level, and blow in from the side at the spacious end, make sure to blow it gently across the fines in the direction of the narrow end.