Diamond Point

The Diamond Point crystal collection site is unique to the area and offers a great recreational opportunity. The geology of Diamond Rim consists primarily of two packages of rocks. The lowest and oldest is granite, that is 1.7 billion years old (Precambrian age rocks) and second, a local metamorphic rock that is slightly older. These rocks are overlain by a sequence of Paleozoic sedimentary rocks (Tapeats layer) containing fossils dating back approximately 530 million years (Cambrian age rocks).  This layer is interpreted to represent ancient shoreline deposits. The boundary between the ancient shoreline layer and underlying Precambrian rocks is a profound unconformity, an ancient erosion surface representing more than 1 billion years of Earth history. Overlying the Tapeats is the Martin Formation dating back 370 million years (Devonian age rocks). The Martin consists of carbonate rocks, sandstone, and shales. The carbonate rocks are a type of sedimentary rock consisting of 2 main types: limestones and dolomites. Both were heavily dissolved by groundwaters while still at depth, creating cavities in the rock within which grew quartz crystals that precipitated from the groundwater. Since these crystals were able to grow unconstrained within an open space within the rocks, many of the quartz crystals developed beautiful crystal shapes and pointy terminations (ends of the crystals). Such crystals that have pointy shapes at both ends are called doubly terminated and this is the collection of quartz crystals, that were loosened from the rock by weathering, for which the Diamond Rim is named. The crystals are locally called Herkimer diamonds, or Payson diamonds, but are very clear quartz crystals, not diamonds. The Martin Formation is overlain by the Redwall Limestone of Mississippian age (330 million years old), and both formations locally contain abundant fossils of creatures that lived in ancient seas or on the sea bottom. The Redwall Limestone is overlain by a sequence of reddish, tan, and gray late Paleozoic layers that are exposed to the north along the Mogollon Rim.

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South of Diamond Rim is a major east-west oriented geologic fault called the Diamond Rim fault. The fault has a complex history, but the latest movement on the fault down-dropped rocks south of the fault relative to those north of the fault. After movement on the fault, the entire area was eroded, removing higher rock layers that are still preserved along the Mogollon Rim to the north. Laying on the surface are more recent deposits, such as stream gravels and angular blocks shed down from the slopes of the Mogollon Rim. 

A special thanks to the Arizona State University School of Earth and Space Exploration for their contributions to their interpretive message of the area’s geology.