14.2.1 Background properties: 'background-color', 'background-image', 'background-repeat', 'background-attachment', 'background-position', and 'background'. This property sets the background color of an element, either a <color> value or the keyword 'transparent', to make the underlying colors shine through.
1 A spiral fracture happens when the break spirals around the bone, which can happen if the bone is twisted. 2  A compression fracture happens when vertebrae in the spinal column are pushed together in an accident or because of osteoporosis.
Like all glass and some other types of naturally occurring rocks, obsidian breaks with a characteristic conchoidal fracture. This smooth, curved type of fracture surface occurs because of the near-absence of mineral crystals in the glass. The intersections of conchoidal fracture surfaces can be sharper than a razor.