Preface
This
month, we are endeavoring to learn more about: Hedenbergite.
A classic pyroxene,
Hedenbergite even occurs in our club's collecting region in Franklin,
New Jersey.
Our exploration is more on the lab characteristics and some world locales. Let's
go!
Introduction
Welcome to
another Mineral-of-the-Month
installment!
Our focus this
month is on: Hedenbergite. This silicate is a pyroxene, and occurs in
various colors, from green to red to black. It sometimes occurs with orange garnets
or
with pink calcites, giving us specimens with the red/green color combination we mentioned
above.
Our author this month is Karissa Hendershot,
a professional geographer, avid fossil
and mineral collector, and accomplished lapidary. Enjoy!
Hedenbergite
By
Karissa Hendershot
THE MINERAL HEDENBERGITE
The
mineral was named after the Swedish chemist, M.A. Ludwig Hedenberg, who first
described the species.
(Source: http://www.galleries.com/minerals/silicate/hedenber/hedenber.htm)
Chemistry: CaFeSi2O6,
Calcium Iron Silicate
Class: Silicates
Subclass: Inosilicates
Group: Pyroxenes
Uses: only as a
mineral specimen.
Specimens
Hedenbergite is a rock forming mineral in several metamorphic rocks, especially contact
metamorphic rocks and skarns. It is also found in some igneous rocks and ore bodies. The
mineral is a part of an important solid solution series of the pyroxene group. The series
includes the minerals diopside,
CaMgSi2 O6, and augite,
(Ca, Na)(Fe, Mg, Al)(Al, Si)2 O6.
Hedenbergite is the iron rich end member of the series. The diopside-hedenbergite series
is
analogous to the amphiobole, tremolite- actinolite
series.
PHYSICAL
CHARACTERISTICS:
Color is black, greenish
black, dark green and dark brown.
Luster is vitreous to
dull.
Transparency crystals are
translucent to opaque.
Crystal System is monoclinic; 2/m
Crystal Habits include short
prismatic (with a square cross section) and accicular, rarely
fibrous crystals. Good crystals are rare, more commonly compact, granular, lamellar and
massive.
Cleavage is perfect in two
lengthwise directions at close to right angles and a basal parting
direction is sometimes seen.
Fracture is uneven to
conchoidal.
Hardness is 5 - 6
Specific Gravity is approximately
3.2 - 3.6 (above average)
Streak is white to pale
green.
Associated Minerals
are wollastonite,
grossular, andradite, magnetite, actinolite, galena,
rhodonite
and calcite.
Occurrence:
common constituent of metamorphosed iron formations or other ferruginous
siliceous sediments; common in Fe-Mn skarns. In alkalic granites, syenites, and in
xenoliths
in kimberlite.
Fluorescence:Translucent to transparent;
light-colored varieties in dolomitic marble may
fluoresce blue or yellow.
Best Field
Indicators are crystal habit,
associations, color, fracture and cleavage.
Composition
Hedenbergite is a member of the
clinopyroxenes, which crystallize in the monoclinic
system and contain calcium, iron, aluminum, sodium, or lithium. The crystals commonly
occur as radiating fibrous aggregates, with stubby, prismatic crystals of nearly square
cross
section being rarer. They are almost opaque except when slivers viewed on the edge.
Fibrous
forms are often greenish-brown in color.
Although usually darker than its gemstone cousin diopside, can still be a wonderful
mineral
specimen. Its dark green to black color can be striking with the bright luster that is
found on
some specimens. While this is not an uncommon mineral, good crystals of hedenbergite are
rare and specimens that show nice crystals, good color and luster are prized.
Occurrence and paragenesis
Found in association with minerals of
contact metamorphism and of regional metamorphism
of dolomitic limestones. Less frequently in rarer types of pegmatites.
The predominant and most abundant Hedenbergite occurrence is at Franklin, where it occurs
as dark green intergrowths with epidote and at Sterling Hill, where it occurs in several
assemblages.
Being Diopside's Fe-analog, Hedenbergite
found in northern New Jersey is greatly magnesian
in content, more closely resembling Diopside.
(Source: http://simplethinking.com/dunn/ch17/hedenbergite.stm)
Distribution:
A few localities for studied
material include: in Sweden, at Nordmark, VÄarmland, and
YxsjÄo, ÄOrebro. From PrÄagraten, Tirol, Austria. At FÄurstenberg, Saxony, Germany.
From RioMarina, Elba, Italy. On Seriphos, Greece. In the USA, at Iron Hill, Gunnison Co.,
Colorado; ¯ne crystals from the Laxey mine, South Mountain, Owyhee Co., Idaho; in the
Pima
district, Pima Co., and the Westinghouse mine, Santa Cruz Co., Arizona; at Hanover, Grant
Co., New Mexico. In the Vesturhorn intrusion, southeast Iceland. Large crystals from
Broken
Hill, New South Wales,Australia. In the Obira mine, Bungo, Oita Prefecture, Japan. At
Tirodi,
Madhya Pradesh, and Kacharwali, Nagpur district, Maharashtra, India. Fine crystals from
the
Skardu area, Pakistan. At Dal'negorsk, Primorskiy Kray, Russia.
The pictures show the different habits that Hedenbergite can take.
Ebay Dealer:
affordableminerals
Ebay
Dealer: socalnevadainc
Ebay
Dealer: d-h-garske
Collected at Tilcon’s Byram Quarry in Stanhope, New Jersey in September 2006.
Broken 1+ inch crystals surrounded by pink calcite and tiny books of Muscovite.
The Calcite can be etched out to reveal complete crystals of the Hedenbergite.
Hedenbergite, University of Delaware
Hedenbergite
at mindat.org
Dr. Bill's Wisconsin Mineral List: Hedenbergite
Alan Guisewite's Hedenbergite Page
Mineral Description: Hedenbergite
Here is where DMS Members can add their
Hedenbergite photos to share with us.
Until Next Time
We hope you have enjoyed our all too short visit to
Hedenbergite. Please join us next month,
for another article, and we shall journey together!
Until then, stay safe, and happy collecting. 
Article Contributors
I would like to gratefully acknowledge the generous
contributions of our fellow Hedenbergite
enthusiasts, collectors, authors, curators, professionals, and club members who made this
work
possible. Thanks.
eBay Dealers: affordableminerals, socalnevadainc, d-h-garske
© 2006 All contributions to this
article are covered under the copyright protection of this article
and by separate and several copyright protection(s), and are to be used for the sole
purposes of
enjoying this scholarly article. They are used gratefully with express written
permission of the
authors, save for generally-accepted scholarly quotes, short in nature, deemed legal to
reference
with the appropriate citation and credit. Reproduction of this article must
be obtained by express
written permission of the author, Kenneth B. Casey, for his contributions, authoring,
photos, and
graphics. Use of all other credited materials requires permission of each
contributor separately .
Links and general contact information are included in the credits above,
and throughout this article.
The advice offered herein are only suggestions; it is the reader's charge to use the
information
contained herein responsibly. DMS is not responsible for misuse or
accidents caused from this
article. All opinions, theories, proofs, and views expressed within this article, and in
others on this
website, do not necessarily reflect the views of the Delaware Mineralogical Society.
Suggested Reading
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About the Author: Karissa is the current President of the Delaware
Mineralogical Society. She is also a member of the Tuscarora Lapidary Society (TLS),
and is an accomplished lapidarist and collector. She also has
affiliations with other mineral and fossil clubs in the eastern United States, and
encourages folks of all ages on the enjoyment of our hobby.
E-mail: kdhendershot@delminsociety.net |
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