How are Different Rock Types Formed

There are three great rock-making processes, namely: sedimentation movements of the melted rock or rock magma from within outwards metamorphism, or transformation of rocks by heat, pressure, and the influence of hot liquids and gases. These will now be discussed in order; and after the description of each process, there follows an account of the … Read more

Classes of Rocks

Three Classes of Rocks.—The rocks are divided into three great classes: Sedimentary rocks, made of fragments of older rocks more or less water worn or ground to powder, and then spread out and deposited in layers of gravel, sand, mud, etc., to be later consolidated by pressure and natural cementing. The material may also consist … Read more

Mechanical Weathering of Rocks

Weathering Forces Under this head are grouped a number of agencies that have their origin in the atmosphere, and which work not only on the surface but as far down as air and water, heat and cold, can penetrate. Because these forces work invisibly, they are apt to be more or less overlooked, although the … Read more

Landforms Created by Glaciers

Origin of Glaciers In temperate and cold climates, and even in tropical countries, where there are very high mountains, the wastage of the snow by melting and evaporation may be less than the snowfall on the tops of the mountains; the snow, therefore, accumulates continually. In cold climates, like that of Greenland, snow accumulates even at … Read more

Types of Formations Caused by Erosion

Forces Causing Erosion It is plain that ever since the crust of the earth became stable enough to allow water to stand, waves to form, rain to fall, and weather to act, these forces have been working on the surface much as they are doing now. It is quite possible that in earlier ages they … Read more

Origin of the Earth

The Earth As a preparation for the systematic study of rocks, it will be useful to look at the earth as a whole, inquiring into its origin, the changes that it has undergone and is still undergoing, and the nature and causes of the great variety of surface features. Origin of the Earth From comparison … Read more

Mineral Identification Tables

The various minerals have been described individually, so that any mineral specimen may be compared with a careful description of that mineral. The prospector’s task is to discover valuable minerals; and to be proficient in this, he must be practised in their identification. The best method of obtaining the requisite experience is to work in … Read more

Sulphate Mineral Group

The group of sulphates correspond to sulphuric acid, H2SO4. In the list of sulphate minerals, there are metals in place of the hydrogen of the acid; they are to be distinguished from sulphides, which contain no oxygen, but are made up of sulphur and metals. Barite or Barytes Barite or Barytes; BaSO4. — Also called … Read more

Phosphate Mineral Group

The Phosphate Mineral Group includes a number of the rarer minerals and apatite. Pitchblende or Uraninite is of Color, pitchy black, greenish, or brownish black; powder, brownish black, grayish, greenish; luster, dull and pitchy, sometimes slightly metallic. H = 5.5; G = 9 to 9.7; no cleavage; contains uranium, radium, etc. Found in pegmatite granite dikes, … Read more

Mica Mineral Types

Mica type minerals make a group of silicates of alumina, with potash, iron, magnesia; characterized by easy cleavage into thin, flexible, elastic sheets. Mica gives off water when strongly heated. Muscovite Muscovite, or white mica, (K,H) AlSiO4, is colorless, sometimes gray, brown, ruby, etc.; powder, white; luster, glassy or pearly; H = 2 to 2.5; G … Read more