Slaty cleavage is a pervasive, parallel foliation (layering) of fine-grained platy minerals (chlorite) in a direction perpendicular to the direction of maximum stress. The process produces the rocks slate and phyllite.
Slaty cleavage refers to the extremely closely spaced, parallel planes of weakness that give a rock like slate its ability to split into very thin, platy layers. Slate is a common roofing material.
A pervasive, parallel foliation of fine-grained, platy minerals (mainly chlorite and sericite) in a direction perpendicular to the direction of maximum finite shortening, developed in slate or other homogeneous sedimentary rocck by deformation and low-grade metamorphism.
Salt, which is also known as the mineral halite, has cleavage in three directions. This causes the salt to break into cubes.
Slaty cleavage often occurs after diagenesis and is the first cleavage feature to form after deformation begins. The tectonic strain must be enough to allow a new strong foliation to form, i.e. slaty cleavage.
SLATY: alignment of microscopic platy minerals – gives a slaty cleavage. PHYLLITIC: foliation of platy minerals that can just be seen with a hand lens. Appears shiny and does not cleave as well because foliation planes may be deformed.
Also known as: slaty foliation.
Cleavage: In mineral terms, cleavage describes how a crystal breaks when subject to stress on a particular plane. If part of a crystal breaks due to stress and the broken piece retains a smooth plane or crystal shape, the mineral has cleavage.
Cleavage is the property of a mineral that allows it to break smoothly along specific internal planes (called cleavage planes) when the mineral is struck sharply with a hammer. Fracture is the property of a mineral breaking in a more or less random pattern with no smooth planar surfaces.
Salt contains the element sodium, which is an essential nutrient needed by the body in small amounts. When salt is added to processed meats, it restructures the proteins, which then act as a binding and emulsifying agent.
Slate is a hard, fine-grained rock with a well-developed rock cleavage or slaty cleavage caused by the incipient growth of platy (micaceous) minerals, due to metamorphism of fine-grained clastic sediments such as shale and siltstone and also volcanic tuffs.
In order of increasing grain size, foliated textures are referred to as SLATY (aphanitic, very fine-grained), PHYLLITIC (aphanitic, fine-grained), SCHISTOSE (phaneritic). The corresponding rock types are called SLATE, PHYLLITE, and SCHIST.
(Metamorphic grade refers to the intensity of metamorphism.) Slate has microscopic clay and mica crystals that have grown perpendicular to the maximum stress direction. Slate tends to break into flat sheets or plates, a property described as slaty cleavage. Figure 10.13 Slate, a low-grade foliated metamorphic rock.
Quartz has crystal surfaces but no cleavage at all. Fluorite forms cubic crystals like those of halite, but it cleaves along planes that differ in orientation from the crystal surfaces.
A mineral can have both cleavage and fracture, and some have either one or the other. Quartz has no cleavage, only fracture. Calcite has no fracture, only cleavage. Feldspar has both.
However, despite the fact that every mineral belongs to a specified crystal system, not every mineral exhibits cleavage. A mineral such as quartz may demonstrate beautiful, well-developed crystals and yet possess no distinct planes of cleavage.
Cleavage serves two main purposes: it forms a multicellular embryo and organizes the embryo into developmental regions. When the outer cells of the blastocyst contact cells lining the uterus, the blastocyst embeds in the lining, a process called implanation.
This can readily be seen in isolecithal eggs, in which very little yolk is present. In the absence of a large concentration of yolk, four major cleavage types can be observed: radial holoblastic, spiral holoblastic, bilateral holoblastic, and rotational holoblastic cleavage.
Early embryonic cell division patterns in vertebrates can be broken into two broad categories, holoblastic cleavage (e.g., most amphibians and mammals) and meroblastic cleavage (e.g., birds, reptiles, and teleost fishes) (Fig.
During cleavage, the cells divide without an increase in mass; that is, one large single-celled zygote divides into multiple smaller cells. Each cell within the blastula is called a blastomere. Cleavage can take place in two ways: holoblastic (total) cleavage or meroblastic (partial) cleavage.