Laccoliths and Pegmatites

Laccoliths
Laccoliths are another huge form of intrusive magma that is able to cover thousands of miles. These are encroached mass of igneous rock that forces apart two strata and forms a round lens shaped mass that is much wider than its thickness. The overlying layers are frequently pushed upward to form a dome. Laccoliths resemble a dome with a slightly curved or a straight bottom. 

Pegmatites
Pegmatite deposits can be found close to other bigger igneous rock deposits. They are usually small and some of them are only a few inches in size, others a few feet and they come in lots of different shapes and looks somewhat lens like. It is not uncommon to find valuable gem crystals in smaller pegmatites such as topaz, garnet, emeralds, beryl, sapphire and tourmaline. The bigger sized pegmatites often times contain fluorine, lithium, niobium, tantalum, uranium as well as some rare earths.