1.8" Grossular Garnets on Hedenbergite - Vesper Peak, Washington

About Vesper Peak Garnets

Vesper Peak, rising above the Sultan Basin in Snohomish County, Washington, is one of the Pacific Northwest’s most celebrated localities for high-quality grossular garnets. The area’s complex contact-metamorphic geology—where intrusive igneous bodies interacted with surrounding carbonate-rich rocks—created ideal conditions for forming vibrant green to orange grossular crystals, many of which occur in attractive calc-silicate assemblages. In addition to garnet, collectors prize the locality for its remarkable diversity of minerals, including quartz, prehnite, diopside, hedenbergite, calcite, clinozoisite, pyrite, and a host of other silicates and sulfides that reflect the varied metamorphic and hydrothermal history of the mountain.

The best-known source on the peak is the 48–55 Mine—often simply referred to as the “Garnet Mine”. Material from this site is noted for its sharp crystal habit, excellent color, and association with contrasting matrix minerals that make for striking display specimens.

Hedenbergite is a calcium iron (magnesium) silicate that often bears a range of green to brown coloration. The crystals are typically opaque and occur in stubby or prismatic aggregates. Inner Mongolia, Russia, and Greece all produce quartz crystals colored green by fibrous hedenbergite inclusions. A variety of hedenbergite can be found in Sweden as well: green-black, blocky crystals come from the Nordmark Odal Field in Värmland County.

Hedenbergite was given its name in 1819 by Jöns Jakob Berzelius, a Swedish chemist. He named the mineral in honor of Anders Ludvig Hedenberg, a chemistry student and co-worker who originally discovered and described the mineral in Tunaberg, Sweden.

The general chemical formula of Hedenbergite is CaFe2+Si2O6 .