This Works Perfect Cleavage Firming Lotion, The Award-Winning Anti-Ageing Moisturiser for Neck and Décolletage, a Youth-Boosting Skin Tightening Cream with Vitamin C, Algae and Larch Extract, 60 ml

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Because over-exposed areas need even more TLC to achieve the smooth, healthy looking skin that perfect cleavage firming lotion gives.

C leavage, fracture, and parting are three related terms that describe how a mineral crystal may break. The orientation and manner of breaking provide important clues about crystal structure and can be keys to mineral identification. If breaking produces planar and smooth surfaces, oriented in a particular way relative to a crystal’s atomic arrangement, we say that the mineral has cleavage. Dodecahedral cleavage occurs when there are six cleavage planes in a crystal. Sphalerite has dodecahedral cleavage.Crystal cleavage is of technical importance in the electronics industry and in the cutting of gemstones. Under ideal circumstances, a cleavage plane might be virtually smooth and flat on an atomic scale. A break in a gemstone that doesn't occur along cleavage planes is either a fracture or a parting. Gemstone Cleavage

Diamond and graphite provide examples of cleavage. Each is composed solely of a single element, carbon. In diamond, each carbon atom is bonded to four others in a tetrahedral pattern with short covalent bonds. The planes of weakness (cleavage planes) in a diamond are in four directions, following the faces of the octahedron. In graphite, carbon atoms are contained in layers in a hexagonal pattern where the covalent bonds are shorter (and thus even stronger) than those of diamond. However, each layer is connected to the other with a longer and much weaker van der Waals bond. This gives graphite a single direction of cleavage, parallel to the basal pinacoid. So weak is this bond that it is broken with little force, giving graphite a slippery feel as layers shear apart. As a result, graphite makes an excellent dry lubricant. [2] Crystal faces and cleavage surfaces may be difficult to tell apart. In some minerals, principal cleavage directions are parallel to crystal faces, but in most they are not. A set of parallel fractures suggests a cleavage, but if only one flat surface is visible, there can be ambiguity. However, this problem is sometimes mitigated because crystal faces often display subtle effects of crystal growth. Twinning (oriented intergrowths of multiple crystals) and other striations (parallel lines on a face), growth rings or layers, pitting, and other imperfections often make a face less smooth than a cleavage plane, and give it lower reflectivity and a more drab luster. 3.71 Calcite from Chihuahua, Mexico Synthetic single crystals of semiconductor materials are generally sold as thin wafers which are much easier to cleave. Simply pressing a silicon wafer against a soft surface and scratching its edge with a diamond scribe is usually enough to cause cleavage; however, when dicing a wafer to form chips, a procedure of scoring and breaking is often followed for greater control. Elemental semiconductors ( silicon, germanium, and diamond) are diamond cubic, a space group for which octahedral cleavage is observed. This means that some orientations of wafer allow near-perfect rectangles to be cleaved. Most other commercial semiconductors ( GaAs, InSb, etc.) can be made in the related zinc blende structure, with similar cleavage planes. The photo seen in Figure 3.71 is of a calcite crystal that shows visible striations on its crystal faces. The lines are artifacts of crystal growth and are not related to cleavage.A mineral may have one or more cleavage planes. Planes that are parallel are considered to be inthe same direction of cleavage and should only count as one. One direction of cleavage is termed basal cleavage. Minerals that display this cleavage will break off in flat sheets. Two directions of cleavage is termed prismatic, while three directions of cleavage at 90°isreferred to as cubic. A mineral with four directions of cleavage is termed octahedral. With 2 or more cleavage planes present, it is important to pay attention to the angle of the cleavage planes. To determine theangle of cleavage, look at the intersection of cleavage planes. Commonly, cleavage planes will intersect at 60°, 90° (right angles), or 120°.

Tendency of crystalline materials Green fluorite with prominent cleavage Biotite with basal cleavage Prismatic cleavage occurs when there are two cleavage planes in a crystal. Spodumene exhibits prismatic cleavage. Basal, pinacoidal, or planar cleavage occurs when there is only one cleavage plane. Talc has basal cleavage. Mica (like muscovite or biotite) also has basal cleavage; this is why mica can be peeled into thin sheets.Rhombohedral cleavage occurs when there are three cleavage planes intersecting at angles that are not 90 degrees. Calcite has rhombohedral cleavage.