Natural Spherical Graphite

One of the most unusual morphologies of graphite is that of spheres that have a radial texture in cross section. Such graphite has long been known to occur in certain cast irons but also occurs naturally in both igneous and metamorphic rocks. Sizes range from microns to centimeters in diameter.
The microstructure of graphite aggregates are well revealed by reflected polarized light microscopy of polished sections.
Click here to see polished sections of spheroidal aggregates from Sterling Hill.

Graphite spheres from Sussex County, New Jersey


Graphite spheres to 1cm in calcite matrix
with franklinite. Probably from the Sterling Hill mine.
E.W. Heinrich collection, Seaman Mineral Museum. JAJ photo.


Section of a 1.5 cm spherical graphite.
Note the radial internal texture.
Seaman Mineral Museum collection, DM1504.

Graphite sphere from the Valentine Mine (#4 Quarry), Harrisville, NY

0.2mm graphite sphere with wollastonite,
etched from gray-white calcite.
John A. Jaszczak collection #1743a and photo.

Spherical graphite from the Pargas (Parainen), Finland

18 micrometer graphite sphere,
etched from calcite. Note the individual hexagonal
graphite crystals on the surface with their basal planes
lying parallel to the surface of the sphere.
John A. Jaszczak collection #1394.
SEM photo by Ruth I. Kramer.

Graphite aggregates of both roses and spheres,
with iron sulfides, etched from calcite.
John A. Jaszczak collection #1394.
SEM photo by Ruth I. Kramer.

Graphite Spheres from Gooderham, Ontario, Canada

1.6mm sphere etched from calcite.
John A. Jaszczak collection #1812 and photo.

Graphite Cuboids from Egan Chute, Ontario, Canada
1-mm cuboids of graphite, associated with spheroidal graphite,
in albite. The cuboid morphology is an influence of
the albite matrix on the graphite aggregates.
John A. Jaszczak collection #2009a and photo.

3-mm Graphite spheres albite.
Goulding-Keene quarry, Egan Chute, Ontario, Canada
John A. Jaszczak collection and photos.

Amygaloidal Graphite from the Oshirabetsu mine, Hiroo, Hokkaido, Japan
Graphite amygdals in gabbro. (right: cut section). John A. Jaszczak collection and photos.

Eudialyte occurrence, Kipawa Complex, Quebec
Graphite spheres to 1 mm in agrellite.
Spheres also occur in associated eudialyte and albite.
John A. Jaszczak collection and photos.

Compare:
  • Molybdenite sphere (1 mm) in fluoriescent sodalite. Mont Saint-Hilaire, Quebec, Canada.
    (Collected by R. Peter Richards)

    REFERENCES

    JASZCZAK, J.A. (1995) Graphite: Flat, Fibrous and Spherical. In, Mesomolecules: From Molecules to Materials. G.D. Mendenhall, A. Greenberg, and J.F. Liebman, editors. (Chapman & Hall, New York) pp. 161-180.

    JASZCZAK, J.A. (1994) On the natural occurrence of spherical graphite. Rocks and Minerals 69, 117-118.

    LEMANSKI, C. (1991) Graphite in ore: An unusual occurrence at the Sterling Hill Mine. The Picking Table 32(1), 11-13.

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