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Collection: (PH) Powderhorn (Iron Hill) Carbonatite Suite -- Gunnison County, SW Colorado
Three hand samples from different facies were collected to represent this sample. Out of two of the largest samples one is a dark fine grained rock while the other is coarse grained. Both contain large (5-8 mm) clusters of biotite.
All weathered faces of the rock show heavy traces of oxidation.
Coarse grained pyroxenite showing heavy traces of oxidation on every weathered face of the rock. Large clusters (5-8 mm) of biotite appear throughout the rock.
Rock is comprised predominately of a dark fine grained matrix. Some specimens have minor amounts of pink K-feldspar. Clusters of biotite (~1 cm in diameter) appear on one face of the rock.
Coarse pyroxenite, with traces of nepheline. This is the freshest pyroxenite that was found. It occurs near the nepheline syenite body in the eastern part of the complex.
Powderhorn Carbonatite Western Minerals Supplementary Materials
OCR PDF of supplemental information for the Powderhorn Carbonatite collection.
Porphyroblasic gneiss (Fenitized)
Fenitized porphyroblastic Gneiss.
Entirely coarse-grained rock except for 2 cm wide dark fine grained band. Obvious traces of oxidation appear on all sides, dominating the most weathered sides of the rock.
Nepheline Syenite. Thin, dark vein runs through the center body of the rock.
Nepheline syenite that outcrops on west side of trail at about 9200 ft. on east side line of section.
The rock is largely comprised of a very fine grained light green matrix with large (1 x 3 cm) black equant galena crystals. It's pretty magnificent.
Large (1 cm-2 cm) dark grey to translucent quartz crystals comprise the matrix of the rock. Melilite minerals propagate consistently paralell to one another throughout the rock.
Composed entirely of Ilmenite.
Rock is comprised almost entirely K-Feldspar.
Recently exhumed ijolite from shallow bulldozer cut.
Hand Sample: Shows traces of iron oxidation in isolated areas. Small (> 0.5 mm in diameter) nodules, with the appearance of small sand grains appear in clusters on one face of the rock (not…
Fenitized Gneiss. Gneiss discovered in direct contact with pyroxenite in prospect trench on ridge, about 500 ft. west of PH-1.. .
Dark gabbro dike separating ijolite and uncompahgrite
Coarse gabbro, extracted from the southern dike of two east-west dikes N of Deldardo Creek.
Evenly distributed dark, light, and white colored coarse-grained (1 mm) crystals. Obvious traces of oxidation from some metallic mineral…
Chert sample found in a Carbonatite.
Pink to light brown chert sample that contains small (< 1 mm diameter) vesicles. Very thin quartz veins propagate through the sample in no preferred orientation.
Iron rich Carbonatite.
Light brown to almost off-white fine grained Carbonatite. Delicated Barite appears in very thin layers on one side of the rock.