Eocene Knightia Fossil Fish

Between 34 to 56 million years ago, during the Eocene Epoch, the subtropical climate in southwestern Wyoming supported life for numerous aquatic species in Lake Gosiute. As a thriving ecosystem with abundant marine plankton, the freshwater lake sustained herring shoals and varieties of predatory fish, stingrays, and crustaceans. Palm trees, crocodiles, and lizards also inhabited the area.

One species of herring, the Knightia, is so plentiful that it later becomes the most common vertebrate fossil discovered anywhere the world. The factors were optimal for perfectly preserving mass amounts of Knightia in a large muddy lake bed with high concentrations of lime. Lake Gosiute, covering an area of fifteen thousand square miles, fluctuated in depth frequently and often exposed its lake bed to dry heat.

Over time, sediment layers flattened under pressure and temperature swings to create large shale and soda ash deposits known collectively as the Green River Formation. Countless, well-preserved fossils have been unearthed from the Green River Formation, including the oldest known flying mammal – an ancient twenty-clawed bat that flew without echolocation.

Almost fifty years ago, the government recognized the historical importance of the vast Fossil Lake and acted to preserve the area itself by declaring it a national monument. The act has helped protect the ancient lake, but opportunistic collectors still seek to exploit the land.

Knightia fossils, though abundant, are a detailed reminder of a very different time in Wyoming’s history when a varying subtropical climate actively preserved life in shale. Today we are able to understand more about the ancient life of Lake Gosiute with thanks to national protection and recognition. It is imperative, for the Green River Formation and fossil beds like it, to keep these areas as fossils themselves and preserved for many generations of people to learn from.

Nevada Opals

Mining for opals is an interesting and rewarding experience even when the deposits can be illusive and difficult to find. This is especially true when prospecting under the desert heat of Nevada and just a little taste is plenty enough to turn an hour excursion into a day's event. Truthfully, it was difficult to walk away from mining at the end of the day even while hot, sweaty, and physically tired from moving overburden all day. The reward was worth it for our first time mining opal; loads of knowledge and beautiful specimens.

Strategy and care is necessary while chipping away at rock that easily crumbles. Going too quickly risks hitting through an opal and fragmenting it into smaller pieces. However, following lines of white silica formation does help to locate the gems and exactly how the specimens pictured here were found. While digging for opals, we also found a few nice specimens of petrified wood well-preserved with ash an silica in tact. We hoped to find a nice example of opalized-wood though we were still thrilled for the discoveries.




Another goal of the day was to find the specimens as pictured, displaying the silica formation and opal deposit tube structure in the rock itself. Often enough opal is shown in an iridescent form, polished, cut, and presented as jewelry. It's really quite amazing how delicate the rock and gems are while surviving thousands and thousands of years. We placed these specimens directly in water when found and let them slowly dry naturally in attempt to preserve the structure.

Pyrite Crystals

The promise of finding gold has too often been thwarted by glittering, multifaceted cuboid crystals known as pyrite. There are stark contrasts between the two minerals when closely examined, but from a distance on a long hot day, it's understandable to see why pyrite could be mistaken for gold. In the right light, pyrite glimmers like gold and easily stands out in piles of excavated dirt. It has fooled many treasure hunters around the world into thinking they finally uncovered something of value for tedious hard work. For this, the reflective mineral acquired the name, Fool's Gold, adding yet another barrier between a man's desire of a lavish lifestyle.

Pyrite is commonly found in areas associated to gold such as quartz deposits and is sometimes known to include very small amounts of gold through a process of substitution. However, the difference in minerals is significant by valuation. Pyrite is formed as a cuboid crystal structure which is distinctly evident upon close inspection. It is also a harder material and this is a reason why people may bite down on the minerals, to assess how malleable the substance is. Gold is softer, easier to work, and a bite will leave an impression when compared to pyrite.


Despite the fact it is desired less than gold, and is not quite as versatile for modern applications, pyrite is still a fascinating mineral. The crystal formation demonstrates nature's ability of creating complex ordered structures under the right conditions. Though it is common to find cuboid shapes in the mineral, pyrite can also be formed with dodecahedron and quasicrystal shapes. Looking closely at pyrite is a glimpse into a window of nature's mathematical capabilities, even if found when expecting to find gold.