The combination of prismatic form and two diamond-shaped directions of cleavage at about 56° and 124° is the diagnostic feature of most members of the amphibole group.
In thin sections, monoclinic pyroxenes are distinguished by two directions of cleavage at approximately 87° and 93°, eight-sided basal cross sections, and light brown or green colour.
In thin sections, amphiboles are distinguished by several properties, including two directions of cleavage at approximately 56° and 124°, six-sided basal cross sections, characteristic colour, and pleochroism (colour variance with the direction of light propagation).
Long prismatic, acicular, or fibrous crystal habit, Mohs hardness between 5 and 6, and two directions of cleavage intersecting at approximately 56° and 124° generally suffice to identify amphiboles in hand specimens.
Within hand specimens, pyroxene can generally be identified by the following characteristics: two directions of cleavage intersecting at roughly right angles (approximately 87° and 93°), stubby prismatic crystal habit with nearly square cross sections perpendicular to cleavage directions, and a Mohs hardness between 5 and 7. Specific gravity values of the pyroxenes range from about 3.0 to 4.0.
Of utmost importance is the determination of the direction of the cleavage, or grain, in the diamond crystal (because of its atomic structure, diamond can be cleaved in four directions parallel to the octahedron crystal faces).
The quantified propensity scale displayed a correlation coefficient of 0.86 with the direction and degree of cleavage site shifts that we observed with 12 mutant substrates cleaved by rhomboid proteases in cellular membranes.
The plethodontid salamander Ensatina eschscholtzii, the largest appropriately studied amphibian egg, has a 6 mm diameter, and has taken a further step in the direction of meroblastic (partial) cleavage.
Our results have expanded our understanding of the importance of the subsurface, in particular the underlying bedrock systems, and the importance of cleavage orientation, as well as topography, in controlling subsurface flow direction in this catchment.
