Garnet Hill, Clark County, Nevada, USAi

Regional Level Types
Garnet Hill	Occurrence (Uncertain)
Clark County	County
Nevada	State
USA	Country

Located about 0.4 miles south of Lake Mead Blvd at the eastern end of Las Vegas, what I have dubbed "Garnet Hill" is an excellent locality to collect Garnet, particularly the Pyrope and Almandine varieties. The hill is filled with Garnet, as the bedrock contains so much that it almost looks like Chicken Pox. Additionally, many of these specimens are euhedral. Erosion deposits south of the hill contain immense amounts of Garnet as well. The site is located approximately 200 feet west of The Great Unconformity.

The Great Unconformity is a site of particular interest geologically for a plethora of reasons, the first being that there is 1.2 billion years missing in the rock record. The unconformity lies between the 540 million year old Cambrian Tapeats Sandstone, and the 1.75 billion year old Precambrian Vishnu Schist, Gneiss, & Granite Complex. The Tapeats Sandstone represents a time that the area was a shallow marine sandy shoal/beach environment, while the Vishnu Group represents a Craton, which is the Igneous/Metamorphic Core of an old continent. In that 1.2 billion years that's missing, the area underwent exclusively erosion- rather than deposition. Unconformities are common and they represent periods of erosion in a locality, but the Great Unconformity is so "Great" because of just how long it was, at 1.2 BILLION years, representing over 1/4 of the entire Earth's existence (Earth is ~4.6 billion years old). If you do the math, 1.2 billion yrs / 4.6 billion yrs x 100% = 26.09%, meaning the Great Unconformity is a gap in the rock record that accounts for 26.09% of the entire time that Earth has existed.

The fact that the Great Unconformity outcrops at the foot of Frenchman Mountain is also a marvel geologically. Frenchman Mountain is a block of Grand Canyon Strata- meaning it is a chunk of the Kaibab Plateau (the plateau the Grand Canyon cuts) that was tilted about 45 degrees and transported 120 kilometers west via strike-slip faulting (The Lake Mead Fault System) beginning during the Miocene Epoch (16 million years ago). There is actually still an active fault that poses a significant earthquake risk to Las Vegas at the foot of Frenchman Mountain, known as the Frenchman Mountain Fault. It is listric and oblique in nature, with both strike-slip and normal dip-slip components to it. Geologic models show the fault to be capable of a Magnitude 7 Earthquake. Luckily, most buildings in Las Vegas are built to Earthquake Code. Moreover, Frenchman Mountain and the Great Unconformity are areas of significant geologic interest because they provide a treasure trove of insight to the geologic history of the Southern Nevada area, and even of the entire North American Continent in general. That particular outcrop on the east side of fabulous Las Vegas, Nevada, provides insight on basically the entire geologic history of the region, combining the rock layers present and the fact that they are where they are and are tilted at how they are tilted.

In conclusion, the Great Unconformity is a site of significant geologic interest for a litany of aforementioned rationales, and Garnet Hill is an excellent locality to collect Garnet just outside of Las Vegas.

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