INTERGROWTHS
Both closely related and completely different minerals are frequently intergrown with each other, and many of the finest specimens of minerals found in museums consist, not of a single mineral, but of a group of minerals which are to some extent intergrown (Plates 4, 7,8, 33, 42, 58, 68). Quite often minerals are joined together or interlocked in an irregular and unpredictable manner. There are, however, quite a number of regular crystal intergrowths which follow a strict pattern of symmetry. In these cases the minerals concerned are closely related and the pattern of intergrowth is due to the similarities in the internal structure of the minerals.