Horse Lake Mountain Hornblende Occurence,
Wenatchee Mining District,
Chelan County, Washington, USA

Hornblende Andesite Intrusions of the Horse Lake Mountain Complex - ~30 Ma[million years ago]
Multiple hornblende andesite intrusions occur within Chumstick Formation sandstone, present in the vicinity of Horse Lake Mountain. As described in Bulletin 75 (DNR, 1983), "abnormally large hornblende phenocrysts ...[with] ... variable habit"
occur within the andesite.

The Black Tuesday Claim is owned and operated by Thea Stender, who is currently mining these world-class specimens.
If you want more information about this locality or are interested in purchasing one of these mined specimens, please visit Thea's Facebook , Instagram, or Etsy pages (Confluence Minerals).

Amphibole (hornblende) - possible magnesio-hastingsite-
NaCa2(Mg4Fe3+)(Si6Al2)O22(OH)2 - Occurs as well-formed black euhedral phenocrysts in light gray andesite.
CaCO3 - Occurs within a centimeter-scale vein crosscutting the andesite, White dogtooth calcite crystals can be found crystallized within the interior of the vein. Smaller second-generation crystals can be found crystallized on the dogtooth crystals. Some crystals are coated with white opal that strongly fluoresce under ultraviolet light.

Amphibole (Hornblende)

Amphibole (Hornblende)
Photo Copyright Joe George
of Cascade Scepters



State of Washington Department of Natural Resources Division of Geology and Earth Resources (DNR), Randall L. Gresens, 1983, Geology of the Wenatchee and Monitor Quadrangles, Chelan and Douglas Counties, Washington, Bulletin 75, scale 1:24,000, 3 plates.