Minerals of the Denny Mountain Skarn, King County, Washington, USA

DENNY MOUNTAIN SKARN
near North Bend, King County, Washington, USA

LOCALITY IMAGES

GEOLOGY
Skarn Deposit, periphery of Snoqualmie Batholith - late Oligocene to early Miocene (28 Ma[million years ago] to 22 Ma).

The Denny Mountain skarn (tactite) deposit is exposed in a deep canyon drainage that flows into Denny Creek. The skarn formed by metasomatism of Jurassic/Triassic age sedimentary rocks during intrusion of the Snoqualmie Batholith.

MINERALS (incomplete list) CLICK for COMPLETE LIST

*Calcite-	CaCO₃ - Massive cystals fill mineralized voids. Etching away the massive calcite often reveals well-preserved mineral species that cystallized before the calcite.
*Garnet(Grossular)-	Ca₃Al₂Si₃O₁₂ - Occurs as translucent to opaque brownish-red dodecohedron
*Hematite-	Fe₂O₃ - Occurs as massive platey aggregates of lustrous silver crystals. Also occurs as terminated rosettes, typically enclosed in calcite.
*Lepidocrocite-	gamma-FeO(OH) - Occurs as mm-scale red inclusions in quartz crystals ("raspberry" scepters).
*Orthoclase(Adularia)-	KAlSi₃O₈ - Occurs as sharp white cystals to about 2 cm with grossular garnet.
*Quartz-	SiO₂ - Occurs as crystals of varying size, quality and habits. Japan-law twins and raspberry scepters (quartz with worm-like lepidocrosite inclusrions) are highly sought after by collectors.
*Scheelite-	CaWO₄ - Occurs as mm-scale golden-yellow pseudo-octahedron associated with other skarn mineralogy. Crystals fluoresce blue under short-wave ultraviolet light.

* photographed

Grossular GARNET
and CALCITE

Raspberry QUARTZ
scepter with
LEPIDOCROCITE
inclusions

HEMATITE rose

Japan Law Twin QUARTZ

Raspberry QUARTZ
scepter cluster with
LEPIDOCROCITE inclusions

SCHEELITE

ORTHOCLASE
(ADULARIA)

REFERENCES (Under Construction)