Lava dating for 24 hours

29-Nov-2017 20:36

This superb 2.85 ct sunstone from Sunstone Butte displays the gem’s most valued attributes: a blend of green and red bodycolor, with reflective spangles of native copper glittering in the interior. No discussion of this topic would be complete without mention of the controversy surrounding treated copper-bearing feldspar; Rossman (2011) provides a chronology.

In the early 2000s, Asian treaters perfected a method of diffusing copper into pale feldspar, flooding the market with low-priced, attractive red and green gems—which destabilized the market for Oregon sunstone.

Past stratovolcanoes of the High Cascades and across Oregon’s remote High Lava Plains lie three sunstone mines (figure 3).

We spent three days there before driving three hours southwest to spend the next two days at the Dust Devil and Sunstone Butte mines.The Steens Basalt of the Oregon Plateau (figure 5), where volcanic flow deposits can contain up to 50% large feldspar crystals (Walker, 1979), erupted around the same time as the more extensive Columbia River basalts further north. This specimen of basalt porphyry from Ponderosa shows a gem-quality sunstone phenocryst surrounded by smaller non-gem feldspar crystals. The High Cascade stratovolcanoes (A) are fueled by subduction under the Pacific Northwest.A porphyry is an igneous rock consisting of large crystals (phenocrysts) in a finer-grained matrix or groundmass. Flood basalts (B) inundated Oregon 15–17 million years ago.These deposits are referred to in the literature as the Lakeview, Lake County, Plush, or Rabbit Basin occurrences.In eastern Oregon, sunstone occurs as basalt flows (see figure 4).

We spent three days there before driving three hours southwest to spend the next two days at the Dust Devil and Sunstone Butte mines.The Steens Basalt of the Oregon Plateau (figure 5), where volcanic flow deposits can contain up to 50% large feldspar crystals (Walker, 1979), erupted around the same time as the more extensive Columbia River basalts further north. This specimen of basalt porphyry from Ponderosa shows a gem-quality sunstone phenocryst surrounded by smaller non-gem feldspar crystals. The High Cascade stratovolcanoes (A) are fueled by subduction under the Pacific Northwest.A porphyry is an igneous rock consisting of large crystals (phenocrysts) in a finer-grained matrix or groundmass. Flood basalts (B) inundated Oregon 15–17 million years ago.These deposits are referred to in the literature as the Lakeview, Lake County, Plush, or Rabbit Basin occurrences.In eastern Oregon, sunstone occurs as basalt flows (see figure 4).We also intend to perform petrographic analyses to characterize the gem-bearing rocks from each deposit and determine their context within the surrounding geology.