What gemstones are in Yellowstone?

Yellowstone National Park is often associated with geysers, hot springs, and dramatic volcanic landscapes, but many visitors also wonder whether gemstones can be found within the park. While Yellowstone is not a commercial gemstone-producing area, it does contain several naturally occurring gem and gem-like materials formed through volcanic, hydrothermal, and sedimentary processes. These stones are scientifically fascinating and historically important, even though collecting them inside the park is strictly prohibited. The gemstones associated with Yellowstone reflect its unique volcanic history and powerful geothermal system rather than the deep crustal processes that create diamonds or precious metals.

Quick Reference: Gemstones Found in Yellowstone National Park

Gemstone / Gem-Like Material	Type	How It Forms in Yellowstone	Typical Colors	Where It Occurs
Obsidian	Volcanic glass	Rapid cooling of silica-rich lava	Black, dark gray, brown	Obsidian Cliff, rhyolite flows
Jasper	Microcrystalline quartz	Silica deposition from hydrothermal fluids	Red, brown, yellow	Limited areas; more common near park margins
Agate	Banded quartz	Silica fills volcanic cavities over time	White, gray, light bands	River gravels near park boundary
Chalcedony	Cryptocrystalline quartz	Precipitation from silica-rich water	White, gray, blue, pale brown	Hydrothermal areas
Quartz Crystals	Crystalline quartz	Slow cooling of silica-rich fluids	Clear, milky, pale colors	Fractures and cavities
Opal (Common)	Hydrated silica	Silica gel deposition from hot water	White, pastel shades	Hot spring terraces
Garnet (Nearby Areas)	Metamorphic mineral	High-pressure crustal metamorphism	Red to dark brown	Beartooth Mountains

Obsidian

Obsidian is the most famous gem-like material found in Yellowstone and is often referred to as a gemstone because of its glassy beauty and sharp, polished appearance. It forms when silica-rich lava cools so rapidly that crystals cannot form, creating a smooth volcanic glass. Yellowstone obsidian is typically black, but it can also appear dark gray or brown depending on trapped gases and mineral impurities. Obsidian from Yellowstone was highly valued by Indigenous peoples for toolmaking, and chemical analysis has shown that it was traded thousands of miles across North America. Although obsidian is not a true mineral, it is widely used in jewelry and decorative objects, making it Yellowstone’s most recognizable gemstone material.

Jasper

Jasper is a variety of microcrystalline quartz associated with Yellowstone’s hydrothermal environments. It forms when silica-rich fluids circulate through volcanic rock and slowly crystallize. Jasper from the Yellowstone region often displays earthy reds, browns, and yellows, colors produced by iron and other trace elements. While jasper is more commonly found in areas surrounding the park rather than within heavily protected zones, it is closely linked to Yellowstone’s geothermal history. Its durability and rich coloration have made it a popular decorative stone throughout human history.

Agate

Agate is another form of quartz related to Yellowstone’s volcanic activity, though it is more commonly found in river gravels and deposits outside the park boundary. Agates form when silica-rich fluids fill cavities in volcanic rock, slowly depositing layers of quartz that can create banded patterns. Yellowstone-area agates are typically subtle in color, often appearing white, gray, or lightly banded rather than brightly colored. Their presence reflects long-term interaction between volcanic rock and mineral-rich groundwater.

Chalcedony

Chalcedony is a fine-grained variety of quartz that forms in similar conditions to agate but without strong banding. In Yellowstone, chalcedony occurs as smooth, waxy-textured nodules associated with silica deposits from hydrothermal fluids. It can appear white, gray, bluish, or pale brown. Chalcedony is significant because it represents one of the most common ways silica is deposited in Yellowstone’s geothermal system, often alongside sinter and other silica-rich formations.

Quartz Crystals

Quartz crystals are present in the broader Yellowstone region, particularly where hydrothermal fluids cooled slowly in fractures and cavities. These crystals form when silica precipitates from hot water and has enough time to grow into well-defined crystal shapes. While large, gem-quality quartz crystals are rare inside the park, smaller crystals and crystal-lined cavities are part of Yellowstone’s mineralogical diversity. Quartz is one of the most abundant minerals on Earth, but in Yellowstone it plays a central role in shaping geyser basins and sinter terraces.

Opal

Opal is sometimes found in association with Yellowstone’s volcanic and hydrothermal environments, though it is usually present in common or non-precious forms rather than gem-quality opal. Opal forms when silica-rich water cools and deposits hydrated silica rather than crystalline quartz. In Yellowstone, opaline deposits contribute to the white and pastel colors seen in some hot spring terraces. While not suitable for jewelry, opal in Yellowstone is scientifically important for understanding how silica moves through geothermal systems.

Garnet in Surrounding Areas

Garnet is not found within Yellowstone’s volcanic core, but it does occur in metamorphic rocks in mountain ranges surrounding the park, such as the Beartooth Mountains. These garnets formed deep in the Earth’s crust under high pressure and temperature, long before Yellowstone’s volcanic activity began. Although these garnets are typically small and not gem-quality, they indicate the presence of ancient metamorphic processes beneath and around the Yellowstone region.