전세계에서 발견 되는 암석으로 된 둥근 공은 지질학적으로 생겨난 것으로 "Concretions" 라 불린다.

[함창우]

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Concretion

From Wikipedia, the free encyclopedia

For other uses, see Calculus (medicine), Enterolith, and Nodule (geology).

Contents

  [hide] 

• 1Origins
• 2Appearance
• 3Composition
• 4Occurrence
• 5Types of concretion
  • 5.1Septarian concretions
  • 5.2Cannonball concretions
  • 5.3Hiatus concretions
  • 5.4Elongate concretions
  • 5.5Moqui Marbles
  • 5.6Kansas pop rocks
  • 5.7Calcium carbonate disc concretions
• 6Gallery
• 7See also
• 8Citations
• 9References
• 10External links

Descriptions dating from the 18th century attest to the fact that concretions have long been regarded as geological curiosities. Because of the variety of unusual shapes, sizes and compositions, concretions have been interpreted to be dinosaur eggs, animal and plant fossils (called pseudofossils), extraterrestrial debris or human artifacts.

Origins[edit]

Detailed studies (i.e., Boles et al., 1985; Thyne and Boles, 1989; Scotchman, 1991; Mozley and Burns, 1993; McBride et al., 2003; Chan et al., 2005; Mozley and Davis, 2005) published in peer-reviewed journals have demonstrated that concretions form after sediments are buried but before the sediment is fully lithified during diagenesis. They typically form when a mineral precipitates and cements sediment around a nucleus, which is often organic, such as a leaf, tooth, piece of shell or fossil. For this reason, fossil collectors commonly break open concretions in their search for fossil animal and plant specimens. Some of the most unusual concretion nuclei, as documented by Al-Agha et al. (1995), are World War II military shells, bombs, and shrapnel, which are found inside siderite concretions found in an English coastal salt marsh.

Depending on the environmental conditions present at the time of their formation, concretions can be created by either concentric or pervasive growth (Mozley, 1996; Raiswell and Fisher, 2000). In concentric growth, the concretion grows as successive layers of mineral precipitate around a central core. This process results in roughly spherical concretions that grow with time. In the case of pervasive growth, cementation of the host sediments, by infilling of its pore space by precipitated minerals, occurs simultaneously throughout the volume of the area, which in time becomes a concretion. Concretions are often exposed at the surface by subsequent erosion that removes the weaker, uncemented material.

Appearance[edit]

Composition[edit]Concretions vary in shape, hardness and size, ranging from objects that require a magnifying lens to be clearly visible to huge bodies three meters in diameter and weighing several thousand pounds. The giant, red concretions occurring in Theodore Roosevelt National Park, in North Dakota, are almost 3 m (9.8 ft) in diameter. Spheroidal concretions, as large as 9 m (30 ft) in diameter, have been found eroding out of the Qasr El Sagha Formation within the Faiyum depression of Egypt. Concretions are usually similar in color to the rock in which they are found. Concretions occur in a wide variety of shapes, including spheres, disks, tubes, and grape-like or soap bubble-like aggregates.

They are commonly composed of a carbonate mineral such as calcite; an amorphous or microcrystalline form of silica such as chert, flint, or jasper; or an iron oxide or hydroxide such as goethite and hematite. They can also be composed of other minerals that include dolomite, ankerite, siderite, pyrite, marcasite, barite and gypsum.

Although concretions often consist of a single dominant mineral, other minerals can be present depending on the environmental conditions which created them. For example, carbonate concretions, which form in response to the reduction of sulfates by bacteria, often contain minor percentages of pyrite. Other concretions, which formed as a result of microbial sulfate reduction, consist of a mixture of calcite, barite, and pyrite.

Occurrence[edit]

Small hematite concretions, dubbed "blueberries" due to their resemblance to blueberries in a muffin, have been observed by the Opportunity rover in the Eagle Crater on Mars. See Martian spherules.Concretions are found in a variety of rocks, but are particularly common in shales, siltstones, and sandstones. They often outwardly resemble fossils or rocks that look as if they do not belong to the stratum in which they were found. Occasionally, concretions contain a fossil, either as its nucleus or as a component that was incorporated during its growth but concretions are not fossils themselves. They appear in nodular patches, concentrated along bedding planes, protruding from weathered cliffsides, randomly distributed over mudhills or perched on soft pedestals.

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일부 음모론가 및 유툽 동영상들은 고대 거인 인류의 유물이다, 또는 외계인이 만들어 놓은 것이다라고 주장합니다.

[milkyway]

취미중 하나가 돌멩이 수집이며 자연광물에 관심 많은지라 유심히 봤습니다.
예전에 외국에서 저런 돌 있다는건 봤지만 한번에 여러 종류의 사진은 처음입니다.

저 원형 돌들이 인공산이냐? 자연산이냐?가 1번째 중요 요소 같고
참고로 아직까지 한국은 물론 동양권에서 발견됐다는 소식은 접한바 없었습니다.

[함창우]

중국에서 발견된 계란형 돌이 있긴 합니다. https://thunderbolts.info/tpod/2007/arch07/070629stoneeggs.htm

[점퍼]

저건 공룡알이 아닐까요~^

[함창우]

안쪽도 돌 입니다.

[함창우]

[milkyway]

손바닥에 안에 쥘 수 있는 돌멩이중 원형과 계란형은 종종 봅니다만
저렇게 큰 것들은 어디에서도 본바 없고
한국의 수석인들이 모으거나 찍은 자연상태 돌작품중에도 저런 사례는 본 기억 없습니다.

저렇게 큰 원형 돌들이 다른 돌들이나 자연물들과 더불어 자연스런 위치에 있었으면 몰라도
보란듯이 덩그라니 홀로 존재하는 경우 보면 인위적 냄새도 좀 나네요.

[안쫄리니쫄티]

동감입니다.