In the old days, people believed gems held magical powers. Gems are very valuable.
Diamond is the hardest naturally occurring substance with a hardness of 10. Its crystal system is cubic because it has 4 equidistant neighboring crystals. Its specific gravity is 3.5. The word diamond means adamas in Greek, meaning “unconquerable”. That’s why Napoleon wanted the Regent, or Pitt diamond set into the hilt of his sword.
Topaz-the name for this substance is a misnomer. The word topaz actually means Zabargad in Greek, which is an island in the Red Sea, a source of peridot. Topaz’s crystal structure is orthorhombic. The hardness of topaz is 8, though it can be broken easily due to its 1 perfect direction of cleavage. The specific gravity is 3.52-3.56, which is very close to diamond’s.
Tourmaline is a very interesting gem. It has a trigonal crystal system and a hardness of 7-7.5. Its specific gravity is 3-3.25. What is really interesting is that if this gem was heated, one side would be positively charged, the other negatively. That’s why there is a watermelon tourmaline. Since it can produce electricity, it has a tendency to attract dust.
Quartz is really just silicon dioxide. Quartz is an igneous rock and its hardness is 7. Its crystal system is trigonal and its specific gravity is 2.65. Quartz is hard to break and has no cleavage. Quartz is the main percentage of dust. Therefore, dust can damage gems with a hardness of 6.99 and lower. Quartz is only pure when it is colorless. Rose quartz has iron and titanium too. Smoky quartz has aluminum.
The Moh’s Scale
The Moh’s Scale is the scale that organizes the rocks in order of hardness with 10 being the hardest and 1 the softest. In other words, diamond is the hardest and talc is the softest. This is an easy way to see which rocks are harder than others.
The Moh’s Scale is not to scale though. Diamond is a lot harder than corundum but corundum isn’t much harder than quartz.
1. Talc
2. Gypsum
3. Calcite
4. Flourite
5. Apatite
6. Orthoclase
7. Topaz
8. Quartz
9. Corundum
10. Diamond
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The land based part of the hydrological cycle is called the Drainage Basin System. A drainage basin is the name given to the area of land which is drained by a river. When water reaches the surface there are a number of routes which it may take in its journey to reach the river. These are shown in the diagram .
Drainage Basins have a number of distinct features . The edge of a drainage basin is characterised by the highest points of land around the river, this is known as the watershed. The point at which a river starts is called its source. As the river continues to flow down stream it may be joined by smaller rivers called tributaries. The point at which these smaller rivers join the main river is known as a confluence. As the river continues its journey, eventually reaches the sea – the point where the river flows into the sea is known as the river mouth.
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