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Hodgkinsonite
Description
Hodgkinsonite is an uncommon mineral found only at
Franklin and Sterling Hill. It generally forms thin seams, small masses of pale violet colored
grains or rough crystals and, of greater interest, fine, brilliant
microcrystals.
The larger microcrystals may have a relatively simple
form development, but can be coated by later generations of minute, more
complexly developed hodgkinsonite microcrystals. All the images below
are from one such sample (Y281).
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Hodgkinsonite.
Franklin, NJ. Width 6 cm. Many of the SEM micrographs on this page are of this sample.
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Hodgkinsonite.
Close-up of vuggy area in sample on left. Franklin, NJ. Width 5 mm.
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| Basic
crystal forms |
Most of the larger hodgkinsonite crystals adopt
the simple habit shown below; dominated by the prism m,{110}, and the pyramid
r, {221}. |
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Pair of intergrown
hodgkinsonite crystals. Field width 0.9 mm.
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Hodgkinsonite
crystal drawing from Palache (1935).
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Minute overgrowths
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Above
left: "Large" hodgkinsonite microcrystal , 0.5 mm high, littered with smaller,
jewel-like hodgkinsonite microcrystals. Above right and below: additional detail of
surface of same crystal.
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Above
left and below right: surface detail of another "large" hodgkinsonite
microcrystal. Above right and lower left: Hodgkinsonite crystal drawings from
Palache (1935).
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| Parallel
growth |
On some samples, the larger hodgkinsonite
crystals show evidence of parallel growth. On this sample, the parallelism is along the c-axis
of the crystals. |
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Above. Hodgkinsonite crystals. Two views of
same cluster. Field width on left 0.5 mm. View on right nearly
perpendicular to crystal c-axes.
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Hodgkinsonite crystal drawing. Projection
along the c-axis. From Palache (1935).
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| Hodgkinsonite
on capillary willemite |
On this sample, a few primary
grains of willemite have been dissolved away (naturally), leaving
small vugs lined with "whisker-like" (capillary) willemite.
On some of these, minute hodgkinsonite microcrystals have formed. |
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Above and below: hodgkinsonite microcrystals
on capillary willemite.
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Left: Detail of previous micrograph. Field
width 0.01 mm. Right: Hodgkinsonite crystal drawings from Palache
(1935).
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