There are many intriguing physical properties to mineral identification. Visible properties include color, luster, streak, crystal form, cleavage. The tactile property can be measured using Mohs scale, which measures hardness of minerals compared to common objects.
Additional tests can be used; including acid, magnetism, smell, taste, and specific gravity. Taking Exhibit A, the most obvious physical property would be to observe its color. It is the least reliable and often misleading property, due to impurities or exposure to the elements.A mineral such as quartz may be colorless, or have various colors. By observing the color, it can be determined if the mineral is mafic or felsic; dark or light. Luster is observing the sample for metallic or non-metallic properties. If metallic, it will reflect light, like gold; if non-metallic, it can be glassy, pearly or dull.
Mineral Identification Essay Example
If Exhibit A is used to draw a line over a pavement, the mineral powder left behind would be referred to as the streak. This can be the color of the rock itself or different. Streak is very important in telling true minerals from fake.For example, gold has a yellow streak, whereas “fool’s gold (pyrite)” has a greenish-black streak (Gardiner and Wilcox 110). Crystal form and cleavage can be viewed using a magnifying glass or sometimes with the naked eye. By observing the sample for crystals, the shapes can be determined; whether cubic, hexagonal or otherwise. If Exhibit A was to be pounded with a hammer, observing the way it broke along the lines of fracture would be observing its cleavage; the direction and angles of fractured surfaces.
Once the visible properties of Exhibit A have been observed, the hardness can be assessed.Hardness of minerals is measured using Mohs scale, as a range, on a scale of one to ten; one (talc) being least hard and ten (diamond) as the hardest. The scale also measures a sample’s hardness relative to common objects. The rationale, if a sample can be scratched by a common object of a known hardness, then it is not as hard as that object. For example, on the scale a nail has a known hardness of 4. 5; so if Exhibit A is scratched by the nail, it can be determined that this sample is softer than a nail.The next common object below that level of hardness would be used; if it is scratched by that object it is softer; and so on.
After evaluating the physical and visible properties of Exhibit A, additional tests can be used in the identification process. These include acid, magnetism, smell, taste, and specific gravity tests. Some minerals, like calcite effervesce when it comes into contact with acid; or like magnetite, it is attracted by a magnet. Further, a mineral such as halite or table salt tastes salty; and some, like sulphur, may have a strong smell.A specific gravity test will measure a mineral’s buoyancy in water and is usually between 2 and 3. “Specific gravity is widely used interchangeably with density… a specific density of 2. 0 indicates that a substance is twice the weight of an equal volume of water” (Sinclair 294).
So Exhibit A has been evaluated, first, by observing its physical properties; color, luster, streak, crystal form and cleavage. Next, its tactile property was assessed to determine its hardness. Lastly, its density, taste, magnetism, smell and reaction to acid were tested.