However, in the same district, pegmatites in the surrounding metamorphic rocks will often have complex mineralogies and carry many exotic phases. This fact has caused much debate. Mineralogy and Zoning Pegmatites fall into two categories, zoned and unzoned. The latter are mineralogically simple, consisting of quartz, feldspar and subordinate mica. They are usually small and almost never of economic significance.
Zoned pegmatites are larger and considerably more complex.
Here again the predominate minerals are quartz and perthitic feldspar, but other mineral phases include muscovite, biotite, apatite, lepidolite, spodumene, beryl, tantalite, columbite, cassiterite, petalite, tourmaline, pollucite, zinnwaldite, uraninite and other minor minerals too numerous to mention. Zoning in this group can be complex, but within a district is remarkable consistent. Studies have shown that the zoned pegmatites have a readily recognizable sequence of zoning and that the zones are nearly concentric within the pegmatite body. Border Zone - Generally has the composition and appearance of an aplite. Rarely exceeds ten centimeters in thickness.