Heckla

Prospect, Inactive

Alternative names

Greenpoint

Commodities and mineralogy

Main commodities Ag; Cu; Mo; Pb; Zn
Other commodities Au
Ore minerals anglesite; chalcopyrite; covellite; digenite; galena; malachite; molybdenite; pyrite; pyrrhotite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale BC
Quadrangle map, 1:63,360-scale A-1
Latitude 56.012
Longitude -130.329
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Heckla prospect, in the southern part of the 12-claim Greenpoint group staked in 1970, is in Section 31 at an elevation of about 4000 feet on the northwest slope of a mountain about 1 mile south-southwest of the confluence of Through and Greenpoint glaciers (Berg and others, 1977, p. 96; Elliott and Koch, 1981, p. 10, loc. 24).

Geologic setting

Geologic description

The country rocks in the area of the Heckla prospect are mainly pelitic hornfels of the Jurassic or older Mesozoic Hazelton Group. Near the prospect, graywacke hornfels is cut by dikes of diorite or andesite that may be apophyses of Triassic Texas Creek Granodiorite, and by felsic dikes that may be apophyses of Eocene Hyder Quartz Monzonite (Berg and others, 1977, p. 15-18, 22-23, 96-97; Smith, 1977; Koch, 1996).
The mineral deposit (Berg, and others, 1977, p. 96-100) consists of five principal quartz fissure veins up to about 4 feet thick. The veins cut graywacke hornfels and minor calcareous schist and contain pyrite, galena, and molybdenite, locally abundant sphalerite and pyrrhotite, sporadic chalcopyrite and a little malachite, and microscopic traces of covellite and digenite. Small amounts of anglesite are in some of the more oxidized zones. Some of the quartz is vuggy and locally iron stained. The wallrock adjacent to the main (Heckla) vein is sheared, altered, and impregnated with sulfides over a width of about 3 feet.
Channel samples of the veins collected in 1972 by the U.S. Bureau of Mines (Berg, 1977, p. 98-99) contain up to 9 percent Pb, 8.5 percent Zn, 1 percent Cu, and 15 percent Mo; assays also show up to 20 oz of Ag and 0.23 oz of Au per ton. Moffit (1927, p. 30) reports that a one-ton test shipment was made in 1925 by 'Hummel, Blasher, and Moss,' which Buddington (1929, p. 102) indicates came from the Heckla prospect. Buddington (p. 101-102) also reports that a picked sample yielded 0.08 oz of Au and 54.3 oz of Ag per ton, 21.6 percent Pb, 32.1 percent Zn, and 4.1 percent Cu.
Lead-isotope studies of the galena at the Heckla prospect (Maas, 1995, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Geologic map unit (-130.33070530251, 56.0116836354232)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Lead-isotope studies of the galena at the Heckla prospect (Maas, 1995, p. 229-248) indicate that the deposit is Eocene in age, contemporaneous with emplacement of the Hyder Quartz Monzonite.
Alteration of deposit Wallrocks adjacent to veins are impregnated with sulfide minerals. Local iron staining. Local oxidation and formation of secondary copper and lead minerals.

Production and reserves

Workings or exploration
Early exploration consisted of a small amount of stripping and excavation of several small, shallow opencuts. Locator of Greenpoint group staked in 1970 explored property by geologic mapping, sampling, some ground geophysics, and shallow diamond drilling.
Early reports describe a picked sample that yielded 0.08 oz of Au and 54.3 oz of Ag per ton, 21.6 percent Pb, 32.1 percent Zn, and 4.1 percent Cu. Channel samples collected by U.S. Bureau of Mines in 1972 contained up to 9 percent Pb, 8.5 percent Zn, 1 percent Cu, and 15 percent Mo; assays also showed up to 20 oz of Ag and 0.23 oz Au per ton.
Indication of production Yes; small
Production notes One-ton test shipment made in 1925.

Additional comments

Five claims staked in 1925. Prospect covered by 12-claim Greenpoint group staked in 1970.
Site is in Misty Fiords National Monument.

References