about pumice site
page title: an Idaho pumice deposit

Pumice is found in abundance all around the world, but a deposit in southeast Idaho is known for being the purest commercial deposit of white pumice on the planet. Hess Pumice Products mines it, refines it, and ships it world-wide.

Nature Formed, Nature Purified

The volcanic eruption that produced the pumice in the southeast Idaho Hess deposit at Wright Creek is nearby, located on the northern shore of an ancient inland sea. What geologists now call Lake Bonneville, this once-vast, now-extinct body of water covered portions of present-day north and central Utah, southern Idaho, and eastern Nevada. For millennia, North America’s biggest lake had no outlet to the ocean, until eventually breaching a point at its northern shore (Idaho’s Red Rock Pass), flooding the Snake River basin—the freed waters churning and gouging the landscape northwest to meet the Columbia River (near present-day Pasco, WA), and then on to the Pacific Ocean. The Great Salt Lake is all that remains of Lake Bonneville.

Researchers have speculated that the Wright Creek pumice deposit is the result of pumice that fell onto the surface of that prehistoric sea and, through centuries of relentless wave action, was washed and agitated and eventually driven into a finger canyon and trapped against the shore, piled wide and deep. The light, foamed-stone pumice spent years churning in the wind-whipped water, which washed the heavy metals and other impurities out, resulting in a naturally clean, naturally pure pumice that is in demand worldwide.01

Physical Characteristics

The table below breaks out the physical properties of the pumice from the Hess deposit in southeast Idaho, USA—a deposit known for its natural purity and whiteness.

Chemical Name: Amorphous Aluminum Silicate
Hardness (MOHS): 6
pH: 7.2
Radioactivity: None
Loss on Ignition (LOI): 5%
Softening Point: 900 Degrees C
Water Soluble Substances: 0.15%
Acid Soluble Substances: 2.9%
Reactivity: Inert (except in the presence of calcium hydroxide or hydrofluoric acid)
Appearance: White Powder
Whiteness GE Brightness of 84

Chemical Characteristics

Pumice from the southeast Idaho Hess deposit is primarily silicon dioxide (SiO2) with a generous splash of aluminum oxide (Al2O3) and small-to-trace amounts of other oxides (see table below). Importantly, no detectable amounts of nasty crystalline-form SiO2.

Silicon Dioxide: 76.2%
Aluminum Oxide: 13.5%
Ferric Oxide: 1.1%
Ferrous Oxide: 0.1%
Sodium Oxide: 1.6%
Potassium Oxide: 1.8%
Calcium Oxide: 0.8%
Titanium Oxide: 0.2%
Magnesium Oxide: 0.05%
Water: <1.0%
Crystalline Si02: None Detected

Shipped Worldwide

Idaho pumice is shipped to industry around the world. Hess Pumice, which mines and refines this special pumice deposit, has years of logistical expertise to ship pumice anywhere by truck, rail, or ocean container. Hess ships pumice to companies in 23 countries—many who have access to pumice from commercial deposits much closer, but the quality and functional result is inferior to the pumice from Idaho.

An Expansive Deposit

Even after actively mining the deposit for more than 60 years, the Hess Wright Creek area pumice mine has a confirmed yield in the millions of tons.

Sourcing Pumice

Hess Pumice Products provides pumice to market at two levels: industrial-use quantities shipped via rail, truck, or ocean container, and small quantities for specific consumer-direct uses via an online Pumice Store backed by a dedicated fulfillment center.


Hess produces a variety of pumice grade and grade blends, from one-inch aggregate to highly refined powders as small as 3 microns. Email salesteam@hesspumice.com (or call 208.766.4777) for expert help with grade selection and logistics.


Sample most of our production grades or purchase branded pumice products for specific applications via an online ordering process.