thumb
Moss agate (also called
mocha stone) is a semi-precious
gemstoneA gemstone or gem is a piece of attractive mineral, which—when cut and polished—is used to make jewelry or other adornments...
formed from
silicon dioxideThe chemical compound silicon dioxide, also known as silica , is an oxide of silicon with a chemical formula of ' and has been known for its hardness since antiquity. Silica is most commonly found in nature as sand or quartz, as well as in the cell walls of diatoms...
. This mineral is commonly found in limestone and granite. It is a form of
agateAgate is a microcrystalline variety of quartz , chiefly chalcedony, characterised by its fineness of grain and brightness of color...
which includes
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
s of a green colour embedded in the
chalcedonyChalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of the minerals quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, whilst moganite is monoclinic.Chalcedony has a waxy luster, and may be...
, forming filaments and other patterns suggestive of
mossMosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
. It also sometimes resembles blue-cheese. The field is a clear or milky-white
quartzQuartz is the second most abundant mineral in the Earth's continental crust . It is made up of a continuous framework of SiO
4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO
2.There are many different varieties of...
, and the included minerals are mainly
oxideAn oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon...
s of
manganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
or
ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
.
Discussion
Ask a question about 'Moss agate' Start a new discussion about 'Moss agate' Answer questions from other users |
thumb
Moss agate (also called
mocha stone) is a semi-precious
gemstoneA gemstone or gem is a piece of attractive mineral, which—when cut and polished—is used to make jewelry or other adornments...
formed from
silicon dioxideThe chemical compound silicon dioxide, also known as silica , is an oxide of silicon with a chemical formula of ' and has been known for its hardness since antiquity. Silica is most commonly found in nature as sand or quartz, as well as in the cell walls of diatoms...
. This mineral is commonly found in limestone and granite. It is a form of
agateAgate is a microcrystalline variety of quartz , chiefly chalcedony, characterised by its fineness of grain and brightness of color...
which includes
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
s of a green colour embedded in the
chalcedonyChalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of the minerals quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, whilst moganite is monoclinic.Chalcedony has a waxy luster, and may be...
, forming filaments and other patterns suggestive of
mossMosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
. It also sometimes resembles blue-cheese. The field is a clear or milky-white
quartzQuartz is the second most abundant mineral in the Earth's continental crust . It is made up of a continuous framework of SiO
4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO
2.There are many different varieties of...
, and the included minerals are mainly
oxideAn oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon...
s of
manganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
or
ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
. Moss agate is of the white variety with green inclusions that resemble moss. It occurs in many locations. The colors are formed due to trace amounts of metal present as an impurity, such as chrome or iron. The metals can make different colors depending on their valence.
Despite its name, moss agate does not contain organic matter and is usually formed from
weatheredWeathering is the decomposition of Earth's rocks, soils and minerals through direct contact with the planet's atmosphere. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice,...
volcanic rockVolcanic rock is an igneous rock of volcanic origin.- Texture :Volcanic rocks are usually fine-grained or aphanitic to glassy in texture. They often contain clasts of other rocks and phenocrysts. Phenocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye...
s.
Montana moss agate is an agate found in the alluvial gravels of the
Yellowstone RiverThe Yellowstone River is a tributary of the Missouri River, approximately long, in the western United States. Considered the principal tributary of the upper Missouri, the river and its tributaries drain a wide area stretching from the Rocky Mountains in the vicinity of the Yellowstone National...
and its tributaries between
SidneySidney is a city in and the county seat of Richland County, Montana, United States, less than 10 mi away from the North Dakota border. The population was 4,774 at the 2000 census. The city lies along the Yellowstone River and is in proximity to the badlands of the Dakotas...
and
Billings, MontanaBillings is the largest city in the U.S. state of Montana, located in the south-central portion of the state. Billings is rapidly growing; as of the 2000 census, the city had a total population of 89,847, while the Census Bureau's 2008 estimate listed the city's population at 103,994. It is the...
. The agate originally was formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity. In Montana moss agate the red color is the result of iron oxide and the black color is the result of manganese oxide.
External links