Crichtonite occurs as small and brilliant crystals of acute rhombohedral habit on quartz at Le Bourg d'Oisans in Dauphine; it agrees closely in composition with the formula FeTiO3 and has a specific gravity of 4.
It crystallizes in the parallel-faced hemihedral class of the rhombohedral system, thus having the same degree of symmetry as phenacite and pyrophanite, but differing from that of haematite.
The angles between the faces are very nearly the same as between the corresponding faces of haematite; but it is to be noted that the rhombohedral angle (94 deg.
Chalybite crystallizes in the rhombohedral system and is isomorphous with calcite; like this it possesses perfect cleavages parallel to the faces of the primitive rhombohedron, the angles between which are 73 deg.
Gmelinite and levynite are other species of zeolites which may be mentioned here, since they are closely related to chabazite, and like it are rhombohedral and frequently twinned.
Crystals are usually rhombohedral in habit, and the primitive rhombohedron r {100} is a common form, the faces being often curved as represented in the figure.
A rhombohedral zeolitic mineral, related in form and composition to chabazite.
It occurs in splendent rhombohedral crystals, and in massive and earthy forms; -- the last called red ocher.
Native magnesium carbonate occurring in white compact or granular masses, and also in rhombohedral crystals.
It is commonly massive, but occurs also in rhombohedral crystals.
Siderite, or spathic iron ore, FeCO3, crystallizes in the rhombohedral system and contains 48.
As in the otherrhombohedral carbonates, the crystals possess perfect cleavages parallel to the faces of the rhombohedron.
It isrhombohedral in crystallization and isomorphous with calcite and chalybite.
A remarkable case of enclosed impurities is presented by the so-called Fontainbleau limestone, which consists of crystals of calcite of an acute rhombohedral form (fig.
The crystals measure up to a yard across, and are rhombohedral or scalenohedral in habit; their faces are usually dull and corroded or coated with stilbite.
The second species, or rhombohedral calamine, is a carbonate of zinc.
In composition it differs entirely from sapphire, or the rhombohedral corundum.
Ivory is distinguishable from bone by its peculiar semi-transparent rhombohedral net-work, which may be readily seen in slips of ivory cut transversely.
A mineral occurring usually in three-sided or six-sided prisms terminated by rhombohedral or scalenohedral planes.
It is a sulphide of antimony and silver, occurring in rhombohedral crystals or massive, and is of a dark red or black color with a metallic adamantine luster.
A sulphide of arsenic and silver of a beautiful cochineal-red color, occurring in rhombohedral crystals, and also massive; ruby silver.
Defn: Native magnesium carbonate occurring in white compact or granular masses, and also in rhombohedral crystals.
Defn: A pyramidal form under the rhombohedral system, inclosed by twelve faces, each a scalene triangle.
Defn: A glassy colorless mineral occurring in rhombohedral crystals, sometimes used as a gem.
Defn: A sulphide of arsenic and silver of a beautiful cochineal-red color, occurring in rhombohedral crystals, and also massive; ruby silver.
Defn: A mineral occurring usually in three-sided or six-sided prisms terminated byrhombohedral or scalenohedral planes.
Defn: A rhombohedral zeolitic mineral, related in form and composition to chabazite.
It is rhombohedralin its crystallization, and thus distinguished from aragonite.
A mineral occuring in glassy rhombohedral crystals, varying in color from white to yellow or red.
The angle between the perfect rhombohedral cleavages is 73 deg.
The rhombohedral division comprises crystals having but three planes of symmetry, intersecting at angles of 120 degrees in the vertical axis.
There are two divisions of the hexagonal system; the hexagonal system properly so-called, and its rhombohedral division.
A fractured surface of this stone displays a multitude of sparkling facets, which are the rhombohedral cleavage-planes of the component grains.
They are colourless and transparent, and are usually traversed by a lattice-work of sharply defined cleavage cracks, which correspond to the rhombohedral faces.
Thus ruby tends to crystallize in flat rhombohedral crystals, while sapphire generally forms in longer, hexagonal prisms.
It crystallizes in the rhombohedral division of the hexagonal system, certain crystal forms being characteristic of the two varieties, ruby and sapphire.
Examples of circularly polarizing cubic crystals are sodium chlorate, sodium bromate, and sodium uranyl acetate; amongst tetragonal crystals are strychnine sulphate and guanidine carbonate; amongst rhombohedral are quartz (q.
Mitscherlich found that therhombohedral angle of calcite decreases 8' 37" as the crystal is raised in temperature from 0 deg.
Hexagonal axes of reference are used: if rhombohedral axes be used many of the simple forms will have two sets of indices.
By some authors these two divisions are treated as separate systems; or again the rhombohedral forms may be considered as hemihedral developments of the hexagonal.
Those with a triad axis are grouped together in the rhombohedral or trigonal division, and those with a hexad axis in the hexagonal division.
A stereographic projection of a rhombohedral crystal is given in fig.
Thus in calcite the rhombohedral angle (the angle between two faces of the fundamental rhombohedron) is 74 deg.
On the other hand, hexagonal forms may be considered as a combination of two rhombohedral forms.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "rhombohedral" in a variety of sentences. We hope that you will now be able to make sentences using this word.
