# Tag Info

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This is not a four- digit number but four separare numbers called Bravais-Miller indices. Bravais-Miller indices descrive the orientation of a crystal plane relative to the symmetry axes of a crystal, as described in Wikipedia. Put very briefly, a zero index means the plane is parallel to that axis, while nonzero indices encode the relative values of the ...

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There are three major types of geological formations that contain or are composed of various rocks: breccia conglomerate xenoliths Breccia The word breccia comes from the Italian word for rubble. There are various forms of breccia: sedimentary tectonic igneous impact hydrothermal The clast (rock fragments) within breccia are angular in shape and ...

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You will probably never know for sure, but the only way to get any confidence is to have any potential specimens analyzed by a mineralogical laboratory that can do Gamma spectroscopy. Fake trinitite, use a variety of means to achieve the glassy green silica look as well as mild radioactivity; however, only trinitite from a nuclear explosion will contain ...

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The idea discussed in the paper you reference is about transferability of Mohs ordinal scale to true hardness. A mineral's ability to scratch is related to it's hardness, but only an indentation test measures absolute hardness (e.g. the Vickers scale). Mineral orientation relative to planar structure can change the result in a scratch test, and two minerals ...

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It may be difficult to ascertain the hardness of a mineral relative to an other mineral in a Mohs streak test if one (or both) are not homogeneous. Already a small local grain of an impurity may put you off; you might remember the occasions of the sudden scratching sound of chalk on the green board. Which is why pen-shaped hardness picks are advantageous: ...

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The rock appears to be a sedimentary rock! The sub-angular nature of the clasts indicate that the rock is a breccia. Based on the color of the matrix, I would suggest that these clasts are bound by a cherty (a form of SiO2) cement. More about Breccia here: https://geology.com/rocks/breccia.shtml It'd be helpful if you could mention the location of the ...

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Dyeing agate is a common practice- the stone is real, but it's been cosmetically altered. The stone gets soaked in a chemical solution, which is absorbed into the microscopic pores in the stone. Whatever dye the person who made these coasters used must have been water-soluble. So, yes, cold water would also cause the pigments to bleed.

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without detailed photographs, I'm in doubt between: Breccia of tectonic origin, probably due to an old cemented fault. The cement looks to me rich in iron, hence the colour. High energy conglomerate, so the hardened sediments of a mass movement (something like a landslide). Nevertheless, I believe it's the second option. There are few blocks that seem too ...

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What you are asking about is mineralogy, a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical ...

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This is the classic description of a porphyry copper-molybdenum deposit. What happens is that there is a magmatic intrusion (the porphyry), which then solidifies. When it solidifies, it expels acidic hydrothermal fluids which carry metals in them - most often copper (represented by chalcopyrite) but also sometimes molybdenum (represented by molybdenite). ...

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The term you are searching for is differentiation. In Early Earth the Crust was mafic. Remelting cycles created an enrichment in silica and alkali elements, forming basalts and granites. As it happens on Continental Crust it is commonly referred as Differentiation of the Continental Crust. Hacker, B.R. et al (2011): "Differentiation of the continental ...

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The short answer: cubic cleavage is a specific example of 3D cleavage. A cleavage plane is a direction along a crystal splits preferentially when exposed to mechanical stress. 3D crystals are objects where the spatial arrangement of atoms is described in a parallelepiped (a unitcell) with three outer dimensions $\vec{a}$, $\vec{b}$, and $\vec{c}$. The ...

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