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A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them.
2009 – The vault particle is an intriguing new discovery of a large hollow particle common in cells, with several different suggestions for its possible biological function. The crystal structures (PDB files 2zuo, 2zv4, 2zv5 [29] and 4hl8 [30]) show that each half of the vault is made up of 39 copies of a long 12-domain protein that swirl ...
Crystallography ranges from the fundamentals of crystal structure to the mathematics of crystal geometry, including those that are not periodic or quasicrystals. At the atomic scale it can involve the use of X-ray diffraction to produce experimental data that the tools of X-ray crystallography can convert into detailed positions of atoms, and ...
Optical properties of common minerals Name Crystal system Indicatrix Optical sign Birefringence Color in plain polars Anorthite: Triclinic: Biaxial (-) 0.013
The following is a list of structure types which appear in the tables above. Regarding the number of atoms in the unit cell, structures in the rhombohedral lattice system have a rhombohedral primitive cell and have trigonal point symmetry but are also often also described in terms of an equivalent but nonprimitive hexagonal unit cell with three ...
This is a list of gemstones, ... Rock crystal (var.) Shocked quartz (var.) Smoky quartz ... Download as PDF; Printable version;
Porphyry can also form even from magma that completely solidifies while still underground. The groundmass will be visibly crystalline, though not as large as the phenocrysts. The crystallization of the phenocrysts during fractional crystallization changes the composition of the remaining liquid magma, moving it closer to the eutectic point ...
In its pure form (rare), it is typically a rose-red colour, [5] but it can also be shades of pink to pale brown. It streaks white, [6] and its Mohs hardness varies between 3.5 and 4.5. Its specific gravity is between 3.45 and 3.6. [7] The crystal system of rhodochrosite is trigonal, with a structure and cleavage in the carbonate rhombohedral ...