Hello,

Sign up to join our community!

Welcome Back,

Please sign in to your account!

Forgot Password,

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

You must login to ask a question.

You must login to ask a question.

Please briefly explain why you feel this question should be reported.

Please briefly explain why you feel this answer should be reported.

Please briefly explain why you feel this user should be reported.

  1. Magmatic Sulfides and Cumulates Mafic and ultramafic magmas, like all common magmas, contain the major elements oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium. But they typically also contain other elements including sulfur, nickel, and less common metals such as platinumRead more

    Magmatic Sulfides and Cumulates

    Mafic and ultramafic magmas, like all common magmas, contain the major elements oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium.

    But they typically also contain other elements including sulfur, nickel, and less common metals such as platinum, palladium, and chromium.

    As these magmas cool and crystallize, the first minerals to form are plagioclase, pyroxene, and olivine – all made of major elements.

    Consequently, the concentrations of sulfur and other minor elements increase in remaining melt.

    Eventually, sulfur concentration becomes great enough so that sulfide minerals begin to crystallize.

    The sulfide minerals, typically containing iron and nickel, may also contain relatively high concentrations of platinum, palladium, and other minor metals.

    Sulfides have greater densities than silicate minerals and the mafic or ultramafic melts.

    So, the denser sulfide minerals will, over time, begin to sink. Eventually, after more cooling and crystallization, significant deposits of sulfide minerals may accumulate on the bottom of a magma chamber.

    The deposits, which may form centimeters-, or meters-thick layer called a cumulate, are often entirely, or nearly entirely, composed of sulfide minerals.

    This process produces magmatic sulfide deposits, which are the most important sources of platinum, palladium, chromium, and several other metals.

    Cumulate sulfide minerals include pentlandite (Fe,Ni)9S8, chalcopyrite (CuFeS2), pyrrhotite (Fe1-xS), and pyrite (FeS2)

    Cumulate sulfide deposits account for almost 60% of the world’s nickel production and more than 95% of platinum and palladium production.

    These deposits are associated with mafic and ultramafic magmas but not, generally, with felsic magmas, because felsic magmas are so viscous that they cool and crystallize before dense minerals can settle.

    Sulfides are not the only kind of mineral that can become concentrated in a cumulate deposit.

    Oxides – including magnetite (Fe3O4), ilmenite (FeTiO3), and chromite (FeCr2O4) – may settle and collect at the bottom of a magma chamber, too.

    These chromite cumulates produce not only significant amounts of chrome, but also very large amounts of platinum, palladium, and related elements.

    See less
  2. 💠Throughout much of human history, many people have been fascinated with gold. 💠 Almost every civilization has prized this special metal. 💠The first question everyone has is “How do I find gold?” After much effort over the millenia, people have developed lots of ways to find that precious metal. 💠SoRead more

    💠Throughout much of human history, many people have been fascinated with gold.

    💠 Almost every civilization has prized this special metal.

    💠The first question everyone has is “How do I find gold?”

    After much effort over the millenia, people have developed lots of ways to find that precious metal.

    💠Sometimes, mother nature herself provides hints about where she is hiding some gold.

    💠One of these natural indicators can be found by looking at the plants and soil where you think gold might be hidden.

    Always remember that gold is rarely found in large chunks.

    💠It will either consist of tiny flakes, or as thin streaks of material within rocks.

    💠 In fact, prospectors refer to the tiny gold flakes found in river sands as “colors.”

    💠Plants Which Might Grow Near Gold

    💠The easiest and most common way of searching for gold is known as placer mining.

    💠 This refers to finding gold found away from its original underground site and moved over time.

    💠 Placer mining is most frequently done either at the bottom of streams or where streams used to flow.

    Cottonwood trees, which grow in wet areas will also grow over top of the areas where streams used to flow.

    💠Although an old stream bed may be dry on the surface, there may still be dampness underground.

    💠Even though the trees don’t necessarily indicate that gold is there, they (or any type of riparian plant for that matter) may help you to locate a placer gold source if you are in gold country.

    💠One of the plants which often grow in areas over gold deposits is the horsetail plant.

    💠Horsetail plants were often used by miners in the past as a guide to where gold might be found.

    💠 It can tolerate the existence of heavy metals in the soil, which has made people believe gold may be nearby.

    💠 Ironically, the horsetail plant also had a practical use for prospectors during the gold rush.

    💠 It was primarily used for washing pots and pans.

    💠The Desert Trumpet is another indicator that helps prospectors know where to look for gold.

    💠 They require more mineralization in the soil than most desert plants.

    💠 The red dirt the Desert Trumpet grows in is likely near heavy metals like gold.

    💠The Trumpet is most commonly found in arid parts of the American Southwest.

    See less
  3. geology, the fields of study concerned with the solid Earth. Included are sciences such as mineralogy, geodesy, and stratigraphy.

    geology, the fields of study concerned with the solid Earth. Included are sciences such as mineralogy, geodesy, and stratigraphy.

    See less
  4. Igneous rocks are formed by the crystallisation of a magma. The difference between granites and basalts is in silica content and their rates of cooling. A basalt is about 53% SiO2, whereas granite is 73%.

    Igneous rocks are formed by the crystallisation of a magma. The difference between granites and basalts is in silica content and their rates of cooling. A basalt is about 53% SiO2, whereas granite is 73%.

    See less
  5. Granitic magma has high levels of potassium and sodium, while basaltic magma has very low levels of these minerals. When magmas are judged by mineral composition like this, they are technically referred to as felsic, which is granitic, and mafic, which is basaltic. Another major difference between tRead more

    Granitic magma has high levels of potassium and sodium, while basaltic magma has very low levels of these minerals. When magmas are judged by mineral composition like this, they are technically referred to as felsic, which is granitic, and mafic, which is basaltic.

    Another major difference between these two types of magmas is the temperature that each needs in order to stay liquid. Felsic magmas are normally between 650 and 800 degrees Celsius, whereas mafic magmas are between 1,000 and 1,200 degrees. This is because the mafic minerals melt at much higher temperatures than potassium and sodium, the felsic minerals. Due in part to the lower temperature, felsic magma is much more viscous than mafic magma, meaning it is much thicker and more resistant to flowing.

    Although basaltic magma can result in basaltic rocks and granitic magma can result in granitic rocks, they can also form other rocks depending on how quickly the magma cools. Granite is formed by the slow cooling of magma within the surface of the earth, while basalt is formed when magma quickly cools after breaching the earth’s surface through volcanic activity.

    See less