Post by 1dave on Dec 28, 2019 20:28:55 GMT -5
The Solar System is OPEN! New material from supernovas is arriving daily. That includes Chromium, arriving in many "irons." Ignored by most {and feared to be mentioned by many} because it is mostly dust, but from time to time . . .
As Chromium is very heavy, most of the original chromium is near the core. The Surface Material has arrived in the last couple of billion years.
Properties of Chromium
Symbol: Cr Atomic Number: 24
Atomic Weight: 51.9961(6)
Melting Point: 2180 K (2453°C, 3464°F)
Boiling Point: 2944 K (3217°C, 4839°F)
Density: 7.14 g/cm3
Chromium is the 18th most abundant element in the Earth's upper crust at 35 ppm (Taylor and McLennen, 1985).
en.wikipedia.org/wiki/Chromium
"Chromium is the fourth transition metal found on the periodic table, and has an electron configuration of [Ar] 3d5 4s1. It is also the first element in the periodic table whose ground-state electron configuration violates the Aufbau principle[/b]
(The aufbau principle, from the German Aufbauprinzip (building-up principle), also called the aufbau rule, states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. For example, the 1s subshell is filled before the 2s subshell is occupied. In this way, the electrons of an atom or ion form the most stable electron configuration possible).
This occurs again later in the periodic table with other elements and their electron configurations, such as copper, niobium, and molybdenum.[10] This occurs because electrons in the same orbital repel each other due to their like charges. In the previous elements, the energetic cost of promoting an electron to the next higher energy level is too great to compensate for that released by lessening inter-electronic repulsion. However, in the 3d transition metals, the energy gap between the 3d and the next-higher 4s subshell is very small, and because the 3d subshell is more compact than the 4s subshell, inter-electron repulsion is smaller between 4s electrons than between 3d electrons. This lowers the energetic cost of promotion and increases the energy released by it, so that the promotion becomes energetically feasible and one or even two electrons are always promoted to the 4s subshell. (Similar promotions happen for every transition metal atom but one, palladium.)[11]"
This occurs again later in the periodic table with other elements and their electron configurations, such as copper, niobium, and molybdenum.[10] This occurs because electrons in the same orbital repel each other due to their like charges. In the previous elements, the energetic cost of promoting an electron to the next higher energy level is too great to compensate for that released by lessening inter-electronic repulsion. However, in the 3d transition metals, the energy gap between the 3d and the next-higher 4s subshell is very small, and because the 3d subshell is more compact than the 4s subshell, inter-electron repulsion is smaller between 4s electrons than between 3d electrons. This lowers the energetic cost of promotion and increases the energy released by it, so that the promotion becomes energetically feasible and one or even two electrons are always promoted to the 4s subshell. (Similar promotions happen for every transition metal atom but one, palladium.)[11]"
Able to attach to other elements with TWO outer rings makes Chromium unusually "grabby," attaching to nearby elements soon after being ejected into space.
Grabbiness also accounts for its self-healing properties that give chrome plating such amazing reflectivity and ability to convert iron into stainless steel.
A few other elements it has grabbed onto:
www.usgs.gov/centers/nmic/chromium-statistics-and-information
pubs.usgs.gov/of/2001/0381/report.pdf
- Handbook of Chemical Economics, Inorganic, Chromium Chapter
Figure 1
Occurrence
Many minerals contain chromium as a major element (see Table 1), and many minerals contain tens of percent chromium. However, only the mineral chromite occurs in large enough quantities to be a commercial source of chromium. Chromite can be found in many different rock types, but the host rocks for economically important chromite deposits are called peridotite and norite. These are distinctive rocks composed mainly of the minerals olivine and pyroxene (peridotite) and pyroxene and plagioclase (norite).
These rocks occur primarily in two types of geologic settings, layered intrusions, which are large bodies of layered igneous rock that cooled very slowly in large underground chambers of molten rock, and ophiolites. Ophiolites are large pieces of the oceanic crust and mantle that have been thrust over continental rocks by the same tectonic forces that cause continental drift. Because chromite deposits in
layered intrusions tend to be tabular in form they are known as stratiform deposits, while those in ophiolites are typically pod-like or irregular in form, are known as podiform deposits. Other sources of chromite are beach sands derived from chromite-containing rocks and laterites that are weathering products of peridotite. Laterites are more widely known as sources of nickel and cobalt. Beach sands and laterites have historically been a minor source of chromite.
Table 2 shows the reserves and resources of chromite worldwide.
INSERT TABLE 1 HERE.
INSERT TABLE 2 HERE.
The identified world resources of chromite are sufficient to meet conceivable demand for centuries. Current world demand is about 12 million metric tons per year. Reserves are that part of identified resources that are currently economic. The reserve base, which includes reserves, is that part of identified resources that are economic now and also may become economic with existing technology, depending on economic conditions and price of chromite.
Stratiform Deposits
Most of the world's chromite resources occur as stratiform deposits in layered intrusions.
1. The Bushveld Complex {Funnel Shaped stratiform! -DC} in South Africa contains over 8.5 billion tons of chromite
while the remainder of the world's economic and subeconomic deposits has a little over 2.5 billion tons,
and about half of that tonnage is in
2. the Great Dyke in Zimbabwe, another layered intrusion (Mineral Commodity Summaries, 1998).
Clearly, chromite resources in layered intrusions are not evenly distributed worldwide. Figure 1 shows the distribution of chromite resources. Other layered intrusions that produce or have produced chromite are:
Stillwater Complex, Montana, USA
Kemi Complex, Finland
Orissa Complex, India
Goias, Brazil
Andriamena, Befandriana, and Ranomena, Madagascar
Mashaba, Zimbabwe
Stratiform deposits are not evenly distributed over geologic time either. While intrusions of the type of rock that carry chromite deposits appear over the spectrum of geologic time, only those of Precambrian age (older than ~560 million years) are known to carry economic chromite deposits; the youngest of these deposits is the Bushveld at about 1.9 billion years. A possible exception to this might be the deposits in the central Ural Mountains, which may be a disrupted layered complex of Early Silurian age (about 440 million years old).
INSERT FIGURE 1 HERE.
Figure 1. Geographic distribution of chromium resources. Chromite deposits are shown by geographic location, deposit size, and predominant deposit type. (Non)Producing determination made in 1997.
Podiform Deposits
Although resources and reserves of podiform deposits are quite small compared to stratiform deposits, podiform deposits have been, and continue to be important sources of chromite. This is because many of these deposits are large and rich enough to be economic. In addition, before some advances in metallurgy, the composition of the chromite produced from podiform deposits was more suited for the metallurgical uses of chromite.
As stated above, podiform deposits occur in ophiolites, which are pieces of the oceanic crust and mantle thrust up over continental rocks. Many different rock types occur in an ophiolite, but the stratigraphically lowest of these is peridotite, which is the host for podiform chromite deposits.
Chromium Chapter - Handbook of Chemical Economics, Inorganic Page 11
Podiformdeposits are found in many places in the world and throughout geologic time. The most important historic sources of chromite from podiform deposits are:
Kempersai, Kazakhstan
Perm district, Russia;
Zambalas, Philippines
Four districts, Albania
Six districts, Turkey
Selukwe, Zimbabwe
New Caledonia
Troodos, Cyprus
Vourinos, Greece
Other production has come from the Appalachians in the United States, Australia, China, Cuba, the former Yugoslavia, Iran, New Guinea, Oman, Pakistan, Sudan, The Coast Ranges in California and Oregon, the Shetland Islands in Scotland, and Vietnam.
Podiform and stratiform deposits have different chemical characteristics, which have determined how they are used. Industry has classified chromite ore as high-chromium, high-iron, and high-aluminum.
Table 3 summarizes the relationship between these classifications, and major use. Table 4 summarizes the range of chemical contents of chromite ores.
INSERT TABLE 3 HERE.
INSERT TABLE 4 HERE.
Beach Sands
Beach sands that contain chromite exist because of a series of geologic facts. Chromite mined from hard rock deposits, either stratiform or podiform, are concentrations in the rock commonly at least 15 volume percent chromite up to 100 percent massive chromite. Some of them are many millions of tons in size. However, all peridotites, even those that do not contain economic concentrations of chromite, contain chromite at low levels, between one and five volume percent of the rock. In addition, peridotite can occur over many hundreds of square miles in ophiolites. The fact that chromite is ubiquitous in peridotite at low
Chromium Chapter - Handbook of Chemical Economics, Inorganic Page 12
levels and peridotite can occur over large areas allows for the possibility of streams moving through peridotite to erode the rock and deposit chromite downstream. In addition, the fact that chromite is the most dense mineral in peridotite means that wave action will naturally concentrate the mineral in a beach environment. Such is the case in Oregon where beach sands were mined during Word War II. Over the last decade, some attempts have been made to mine sands on the island of Palawan in the Philippines.
Other sand, or placer chromite deposits occur in Indonesia, Papua New Guinea, Vietnam, and Zimbabwe.
Laterites
Laterite forms as the result of weathering of peridotite in a tropical or a forested, warm temperate climate. Laterite is a thick red soil derived from the rock below. It is red because of the high concentration of iron. The process of laterization leaches out most of the silicate minerals in the rock, leaving higher concentrations of elements that can fit in the structures of non- silicate minerals. Thus latentic deposits concentrate elements such as iron, nickel, cobalt, and chromium. In some laterites chromite is concentrated to economic concentrations. This is the case in Indonesia where chromite is being mined.
Many minerals contain chromium as a major element (see Table 1), and many minerals contain tens of percent chromium. However, only the mineral chromite occurs in large enough quantities to be a commercial source of chromium. Chromite can be found in many different rock types, but the host rocks for economically important chromite deposits are called peridotite and norite. These are distinctive rocks composed mainly of the minerals olivine and pyroxene (peridotite) and pyroxene and plagioclase (norite).
These rocks occur primarily in two types of geologic settings, layered intrusions, which are large bodies of layered igneous rock that cooled very slowly in large underground chambers of molten rock, and ophiolites. Ophiolites are large pieces of the oceanic crust and mantle that have been thrust over continental rocks by the same tectonic forces that cause continental drift. Because chromite deposits in
layered intrusions tend to be tabular in form they are known as stratiform deposits, while those in ophiolites are typically pod-like or irregular in form, are known as podiform deposits. Other sources of chromite are beach sands derived from chromite-containing rocks and laterites that are weathering products of peridotite. Laterites are more widely known as sources of nickel and cobalt. Beach sands and laterites have historically been a minor source of chromite.
Table 2 shows the reserves and resources of chromite worldwide.
INSERT TABLE 1 HERE.
INSERT TABLE 2 HERE.
The identified world resources of chromite are sufficient to meet conceivable demand for centuries. Current world demand is about 12 million metric tons per year. Reserves are that part of identified resources that are currently economic. The reserve base, which includes reserves, is that part of identified resources that are economic now and also may become economic with existing technology, depending on economic conditions and price of chromite.
Stratiform Deposits
Most of the world's chromite resources occur as stratiform deposits in layered intrusions.
1. The Bushveld Complex {Funnel Shaped stratiform! -DC} in South Africa contains over 8.5 billion tons of chromite
while the remainder of the world's economic and subeconomic deposits has a little over 2.5 billion tons,
and about half of that tonnage is in
2. the Great Dyke in Zimbabwe, another layered intrusion (Mineral Commodity Summaries, 1998).
Clearly, chromite resources in layered intrusions are not evenly distributed worldwide. Figure 1 shows the distribution of chromite resources. Other layered intrusions that produce or have produced chromite are:
Stillwater Complex, Montana, USA
Kemi Complex, Finland
Orissa Complex, India
Goias, Brazil
Andriamena, Befandriana, and Ranomena, Madagascar
Mashaba, Zimbabwe
Stratiform deposits are not evenly distributed over geologic time either. While intrusions of the type of rock that carry chromite deposits appear over the spectrum of geologic time, only those of Precambrian age (older than ~560 million years) are known to carry economic chromite deposits; the youngest of these deposits is the Bushveld at about 1.9 billion years. A possible exception to this might be the deposits in the central Ural Mountains, which may be a disrupted layered complex of Early Silurian age (about 440 million years old).
INSERT FIGURE 1 HERE.
Figure 1. Geographic distribution of chromium resources. Chromite deposits are shown by geographic location, deposit size, and predominant deposit type. (Non)Producing determination made in 1997.
Podiform Deposits
Although resources and reserves of podiform deposits are quite small compared to stratiform deposits, podiform deposits have been, and continue to be important sources of chromite. This is because many of these deposits are large and rich enough to be economic. In addition, before some advances in metallurgy, the composition of the chromite produced from podiform deposits was more suited for the metallurgical uses of chromite.
As stated above, podiform deposits occur in ophiolites, which are pieces of the oceanic crust and mantle thrust up over continental rocks. Many different rock types occur in an ophiolite, but the stratigraphically lowest of these is peridotite, which is the host for podiform chromite deposits.
Chromium Chapter - Handbook of Chemical Economics, Inorganic Page 11
Podiformdeposits are found in many places in the world and throughout geologic time. The most important historic sources of chromite from podiform deposits are:
Kempersai, Kazakhstan
Perm district, Russia;
Zambalas, Philippines
Four districts, Albania
Six districts, Turkey
Selukwe, Zimbabwe
New Caledonia
Troodos, Cyprus
Vourinos, Greece
Other production has come from the Appalachians in the United States, Australia, China, Cuba, the former Yugoslavia, Iran, New Guinea, Oman, Pakistan, Sudan, The Coast Ranges in California and Oregon, the Shetland Islands in Scotland, and Vietnam.
Podiform and stratiform deposits have different chemical characteristics, which have determined how they are used. Industry has classified chromite ore as high-chromium, high-iron, and high-aluminum.
Table 3 summarizes the relationship between these classifications, and major use. Table 4 summarizes the range of chemical contents of chromite ores.
INSERT TABLE 3 HERE.
INSERT TABLE 4 HERE.
Beach Sands
Beach sands that contain chromite exist because of a series of geologic facts. Chromite mined from hard rock deposits, either stratiform or podiform, are concentrations in the rock commonly at least 15 volume percent chromite up to 100 percent massive chromite. Some of them are many millions of tons in size. However, all peridotites, even those that do not contain economic concentrations of chromite, contain chromite at low levels, between one and five volume percent of the rock. In addition, peridotite can occur over many hundreds of square miles in ophiolites. The fact that chromite is ubiquitous in peridotite at low
Chromium Chapter - Handbook of Chemical Economics, Inorganic Page 12
levels and peridotite can occur over large areas allows for the possibility of streams moving through peridotite to erode the rock and deposit chromite downstream. In addition, the fact that chromite is the most dense mineral in peridotite means that wave action will naturally concentrate the mineral in a beach environment. Such is the case in Oregon where beach sands were mined during Word War II. Over the last decade, some attempts have been made to mine sands on the island of Palawan in the Philippines.
Other sand, or placer chromite deposits occur in Indonesia, Papua New Guinea, Vietnam, and Zimbabwe.
Laterites
Laterite forms as the result of weathering of peridotite in a tropical or a forested, warm temperate climate. Laterite is a thick red soil derived from the rock below. It is red because of the high concentration of iron. The process of laterization leaches out most of the silicate minerals in the rock, leaving higher concentrations of elements that can fit in the structures of non- silicate minerals. Thus latentic deposits concentrate elements such as iron, nickel, cobalt, and chromium. In some laterites chromite is concentrated to economic concentrations. This is the case in Indonesia where chromite is being mined.
