SEM / MICRO GALLERY
Introduction
Micro-mineral collecting
Selected species
Barysilite, ganomalite, kentrolite
Willemite & tephroite
Hodgkinsonite
[others if requested !]

 

> introduction

Introduction to Franklin micro-minerals

Franklin minerals are even more amazing under a microscope. The rocks from these deposits have had a long and complex history, and there are many periods of crystal growth best studied under a microscope.

Olympus stereo-zoom microscope

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Vugs, or open cavities, are frequently found in Franklin-Sterling samples which contain coatings of minute, millimeter-sized and smaller, micro-crystals.

Vug containing micro-crystals of zincite, barite, fluorite and chlorophoenicite in a sample of massive franklinite-willemite ore. Franklin, NJ. Width 5 cm.

These crystals are often exquisitely formed, showing the greatest degree of perfection, and complexity of crystal forms, of any of the many crystallized specimens known from the district.

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Magnified view of above sample.
Width 8 mm.

Though much of the beauty of such micro-crystallized specimens can be seen using a simple light stereomicroscope, such as figured above, the scanning electron microscope offers an even more amazing (if monochrome) view.

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SEM view of fluorite and chlorophoenicite from sample shown above. Width 0.5 mm

What is SEM ?

SEM stands for scanning electron microscope, a principal research tool for the study of surfaces at high magnification.

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Samples are placed in an evacuated chamber and bombarded by a carefully focused beam of electrons, and the secondary electrons are collected, amplified and used to form an image, typically on a television screen, of the sample's surface.

Details smaller than one-tenth of a micron are routinely visible with most machines. Samples are generally first made conductive through a microscopic coating of carbon or a special metal alloy. No colors and no internal structures are visible using SEM, but superb surface images can be easily prepared.

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A large number of Franklin-Sterling Hill minerals occur in secondary micro-crystals, and these are often exquisitely formed. Such samples provide fascinating material for detailed SEM study.

Take a look at some of the SEM images listed at upper left under 'selected species'.

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