Very few minerals are magnetic and will attract a magnet. Such minerals will als
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Question
Very few minerals are magnetic and will attract a magnet. Such minerals will also deflect the magnetic needle of a compass. Name one such mineral?
Why can we describe the ocean as containing a lot of dissolved gypsum, when you observed that little gypsum dissolved in your container?
How many of the six dominant substances in seawater are present in the mineral samples?
What types of scientist should be consulted before engineers start to build a dam and why (i.e. what kinds of information would engineers hope to learn from these scientists)?
Explanation / Answer
1)The Magnetic Minerals are few, but the property is important because of this fact. Once a specimen is established as magnetic, identification becomes a rather routine exercise. The mineral magnetite is named after this characteristic. Magnetism occurs (most often) when there is an imbalance in the structural arrangement of the iron ions. Iron is found in two principle ionic states called ferrous and ferric ions. The ferrous ion has charge of positive two, (+2); the ferric ion has a charge of positive three, (+3). The two ions have different atomic radii because the higher charge of the ferric ions pulls the electrons surrounding the ion in tighter. This fact can lead to the different ions being placed in separate positions in a crystal structure. Electrons that move from the ferrous to the higher positively charged ferric ions create a slight magnetic field. The minerals that are magnetic range in magnetic strength from being capable of lifting steel rods to barely turning the needle on a compass. A few minerals may not be magnetic, but are still attracted to magnets. Magnetism is somewhat of an unreliable property as not all specimens may demonstrate it. While the presence of magnetism may all but clinch an identification, the lack of magnetism should not generally exclude typically magnetic minerals. A compass needle is a good test device for testing magnetism as is a magnet on a string that might sway near the specimen. Iron and steel will be attracted by a magnet. These metals will also defl ect a compass needle, but metals such as aluminum and copper won’t. The (rare) mineral native iron and iron found in meteorites are strongly attracted by a magnet. (Iron meteorites are mostly nickel-iron; many stony meteorites also have small blebs of nickel-iron scattered throughout their interiors.) Iron, steel, and nickel-iron are magnetizable, meaning they can be made magnetic. For instance, stroking an iron paper clip a hundred times in the same direction with a strong magnet will make the paper clip into a magnet – the clip can then be used to pick up other paper clips. You will fi nd that magnetite will defl ect the compass needle. Some magnetite crystals are much more strongly magnetic than others. Lodestone is massive magnetite and by defi nition is strongly magnetic. Frequently, lodestone samples will be found covered with a black “fuzz.” This magnetic fuzz consists of small chips or dust from the lodestone and/or small metal fi lings. Additional possibilities: Magnetite and maghemite are strongly magnetic. Minerals that are weakly magnetic include chromite, franklinite, ferberite, siderite, tantalite, babingtonite, and ilmenite. Pyrrhotite specimens are erratic: some are strongly magnetic others are weak. Some specimens of hematite may be magnetic, too. This may be because they are really mislabeled magnetite, or it could be because small amounts of magnetite are intermixed with the hematite. Limonite may form from weathered magnetite and a residue of unaltered magnetite may render some limonite specimens magnetic. Several minerals react when placed within a magnetic field. Some minerals are strongly attracted to the magnet, others are weakly attracted, and one mineral is actually repelled. There are also several minerals that are attracted to magnetic fields only when heated. A magnetic field is an area encompassinga magnet or electrical current that has the ability to attract or repel certain objects placed in the field. The closer the object is to the magnet or electrical current, the more powerful the magnetic effect. In virtually all cases, the presence of the element iron as a component of the mineral's chemical structure is responsible its magnetic properties. Magnetic properties of minerals are defined as follows:Ferromagnetism describes strong attraction to magnetic fields. This property is exhibited in few minerals, notably Magnetite and Pyrrhotite. Paramagnetism is weak attraction to magnetic fields. The attraction is usually discernible, but it may be so weak that it is undetectable. Most paramagnetic minerals become strongly magnetic when heated. A small number of paramagnetic minerals, such as Platinum, are not essentially paramagnetic, but contain iron impurities which are responsible for the paramagnetism. However, some specimens lacking iron also exist, and these are not paramagnetic. Some examples of paramagnetic minerals are Hematite and Franklinite.
Diamagnetism. Only one mineral, Bismuth, is diamagnetic, meaning it is repelled from magnetic fields. Another property, which is unnamed, is attraction to magnetic fields when heated. Some iron sulfides and oxides become ferromagnetic after heating, as a result of combined sulfur or oxygen ions freeing themselves from the iron. Some minerals may even act as magnets when heated.
Magnetism. Only a variety of one mineral acts as a magnet, generating magnetic fields on its own. This mineral is Lodestone, the magnetic variety of Magnetite, which found in only a few deposits throughout the world. Although it is only weakly magnetic, its magnetism is definitely discernible
Magnetic properties are useful for identifying a mineral, for if observed it can pinpoint a mineral. The most effective testing results are obtained with the use of a powerful magnet. The only minerals that possibly respond to magnets without heating are opaque, metallic-looking minerals2) Sea water contains about 35 grams per kilogram of dissolved salt. The most obvious source for the salt is river water, which can easily be observed weathering rocks (from which the water derives minerals), carrying sediment, and flowing continually into the ocean.*Because the water added to the ocean evaporates but the dissolved salts do not, it seems reasonable to suggest that river water brings salt to the ocean. But a closer look shows that the process must be more complicated. Table 1 compares the major substances dissolved in river water and ocean water. If sea water is simply concentrated river water, these elements should be present in the same ratios in both types of water. For both water types, the Cl/Cl ratio is 1 because that is the chosen standard of comparison. Notice that the ratio patterns for most components for the two water types are quite different. This pattern means that simple evaporation of water cannot change river water into sea water.
Addition–Removal Processes and Considerations
The composition of sea water is controlled by many different processes, all acting at the same time, and adding and removing substances at different rates (see figure). The sum of all the processes, a kinetic (changing) balance, determines sea-water chemistry (see Table 2 on page 136).
When sea water dries up completely, it leaves behind a salt deposit called an evaporite. Evaporites of greatly different ages on Earth all are similar, so the conclusion that sea water must have had roughly the same chemistry over hundreds of millions of years If this is true, then all the processes affecting sea-water chemistry must be at steady state—that is, operating so that the input of salt equals the output. For a steady-state ocean, it is possible to find out how long a particular element stays in the ocean (i.e., its residence time) before it is removed. The ocean is at steady state for a particular element if that element is added and removed at the same rate.
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