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| Geology-Bits |
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Geobits
includes an assortment of geological items that are posted periodically. |
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| This
issue of GEOBITS of hardness, Jade is contributed
by Mr. William Chow; Garnet and Quartz Varieties
is contributed by Dr. L.S Chan. For more information, follow
the links to the pages for details of each topic. |
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| GEOBITS
of Jade: |
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Jade
is popular among Chinese. In gemmology, however, only
two minerals are recognised as jade: nephrite and jadeite.
Many jades sold on the market are treated to enhance their
beauty. The tests described here are by no means exclusive
but are some of the common means for differentiating various
kinds of jade.
Mass
of prismatic bluish green colored Johannsenite crystals.
N'Chwaning Mine, Kalahari Manganese Field, Northern
Cape Province, South Africa.
Click
to the LINK for more detail on Jade.
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Jade
crystals
7.2
x 4 cm.
Photo by John Veevaert
Source: http://webmineral.com/specimensG.shtml |
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| GEOBITS
of Garnets:
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ome
of these rare gamets are, so far, extremely
rare: Majorite has only been found
in meteorites, and several others have been found in
just a very few locations -
Click
to the LINK for more detail on Garnet
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| GEOBITS
of Quartzs:
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How
many varieties of quartz do you know?
Quartz, a silica and the most common mineral, can occur
in many forms. It
can be ultra-fine grained (cryptocrystalline) or appears
with an extraordinary colour when it contains certain
elements or impurities. The charts below are some of the
most common varieties of quartz. Some high-pressure forms
of quartz such as coesite and stishovite are rare in nature
and high-temperature forms such as tridymite and cristobalite
can be identified only with a microscope.
Click
to the LINK for more detail on Quartz Varieties. |
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Mohs’
Hardness Scale is a useful mean for mineral identification
in field. Although it cannot determine the absolute
value of hardness of individual minerals, the principle
of comparing soft and hard materials helps to eliminate
many possibilities of like minerals. Field geologists
always carry a hardness box in work. Do you want to
get one, in Do-It-Yourself way?
Click
to the LINK for more detail on "Hardness Box DIY"
Source:
http://realgar.mcli.dist.maricopa.edu/aaim/linear/calcite.gif
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