mineral- naturally occurring inorganic solid substance with a definite soil substance with a definite chemical composition and structure
rock- a group of minerals bound together
color- first and most easily observed mineral property
luster- way the mineral shines in reflected light
streak- the color of a mineral when powdered or rubbed on a streak plate
hardness- the resistance of a mineral scratching
cleavage-the tendency of mineral to split easily along planes parallel to the crystal faces, leaving smooth, flat surfaces in one or more directions
crystal shape- the pattern mineral's ions or atoms form if there is enough time and room to grow
specific gravity- the ratio ...view middle of the document...
1. (b) Minerals in rocks are usually identified by their physical properties.
2. (a) Color is the least useful property for mineral identification. One reason is that many different minerals have similar colors. Also, traces of impurities can turn colorless minerals into colored minerals. A third reason is that some minerals change color when exposed to air.
(b) The luster of mineral is the way of the mineral shines in reflected light. Lusters are either metallic or nonmetallic. Examples of minerals with metallic luster are galena and pyrite. A mineral that doesn't shine like a metal has a nonmetallic luster. A vitreous luster, shinning glass, is seen in quartz.
(c) Crystal shape is not usually helpful in mineral identification because crystal faces are rare. More often mineral grains in rocks lacked room to grow. The mineral grains in most rocks are so small or so imperfect that crystal faces are hard to find.
3. (a) The streak of a mineral is the color of its powder. The streak is obtained by rubbing the mineral on an unglazed white tile, called a streak plate. For many minerals, the streak is not the same color as the mineral. Although the color of a mineral may vary, its streak rarely does. As a rule, the streak of a metallic mineral is at least as dark as the hand specimen. The streak of a nonmetallic mineral is usually colorless or white.
(b) The cleavage of a mineral is its tendency to split easily or to seperate along flat surfaces. Cleavage surfaces can be obsereved even on tiny mineral grains. Mica splits very easily, and always in the same direction. Mica is said to have one perfect cleavage. Feldspar splits readily in two different directions, at or near right angles. Calcite and galena cleave in three directions.
(d) The hardness of mineral is its resistance to being scratched. It will scratch any other mineral againts which is rubbed. From Moh's scale you can find the approximate hardness of any common mineral. All you need is a copper penny, a knife blade or metal nail file, and a small glass plate. If a mineral is harder than number 5 but softer than number 6 in the hardness scale, it has a hardness about 5 1/2.
4. (a) Specific gravity is another property that is helpful in identifying a mineral.
Specific gravity= weight of sample in air/weight of equal volume of water
(b)Nearly all minerals are denser than water. Their specific gravities are greater than 1. Typical nonmetallic minerals have specific gravities of about to 5. Other metallic minerals are much denser. Gold has specific gravity as high as 19.3 when pure.
5. Calcite is the principle mineral in limestone and marble. Calcite is easily identified by simple chemical test. Calcite is calcium carbonate. If a drop of cold, weak hydrochloric acid is placed on calcite, the drop of acid fizzes. The bubbles are carbon dioxide gas. Other minerals also react to acid, but they are not reactive. They may require using stronger acid, heating the...