| Some minerals do not cleave in any definite pattern. When they break randomly these minerals are said to 'fracture'. |
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| When obsidian (right) breaks it produces a shell-like pattern called a 'conchoidal fracture'. Remember this pattern. It's typical of minerals that fracture. |
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At left, coal, also fractures but it doesn't show the conchoidal pattern. Coal simply shatters into randomly shaped pieces. |
