stone.pdf
Transcript of stone.pdf
WHAT IS A PRECIOUS GEM STONE
AND SEMIPRECIOUS?
A gem is a naturally occurring material desirable for
its beauty, valuable in its rarity, and
sufficiently durable to give lasting pleasure.
Semi-precious stones are usually softer and less valuable, and thus not as rare as precious gems. the mineral olivine has a semi-precious variety called peridot
Peridot is one of the few gemstones that occur in
only one color, an olive green. The intensity and
tint of the green, however, depends on how much
iron is contained in the crystal structure, so the
color of individual peridot gems can vary from
yellow- to olive- to brownish-green. The most
valued color is a dark olive-green.
JADEITE – MORE THAN $3 MILLION PER CARAT
The more intense the green, the more expensive the stone will get. The Chinese, however, also value the white jadeite with green spots. A deep blue-green jadeite that emits a translucent hue has also been discovered in recent times in Guatemala.
There are two major exceptions to the rule:
Because of their rarity are considered to be
precious Opal and Pearls.
OPALS
The main reasons for this
is the very high demand
and the fact that truly
magnificent black opals
are only a fraction of the
total black opal
production. High quality
black opal sells for around
$2,000 per carat, though
prices of $5,000 and higher
are not unheard of.
It is important to distinguish where gems
are formed from where they are found. Gems are not
always found where they were formed, nor are they
formed where they're found.
Almost all gems are formed below the Earth's
surface.
WEATHERING OF ALL TYPES OF ROCKS YIELDS SEDIMENTS THAT ARE
DEPOSITED IN A WIDE VARIETY OF ENVIRONMENTS, SUCH AS STREAMS
AND RIVERS, SHORELINES, ALLUVIAL FANS, AND DELTAS
Guyana: In the first half of the 20th century
miners, employing primitive methods, recovered
significant quantities of gem-quality diamonds
from the rivers and streams. In fact the two
largest gem-quality diamonds recovered in to
date - 56.75 carats and 25.67 carats.
VALUE
The 4 C'S factors:
Color: Some colors are more desirable than
others.
Clarity: flaws (crack, inclusions) decrease the
value of a gemstone.
Cut: Poorly cut stones have much lower value.
Carat weight:
THE REASON WHY GOLD WILL TAKE THIS PATH IS BECAUSE OF THE FLOW OF WATER
DURING A STORM – A RIVER THAT IS RUNNING AT ITS NORMAL RATE OF FLOW DOES
NOT HAVE ENOUGH POWER AND FORCE TO MOVE GOLD FROM WHERE IT CURRENTLY
LIES, IT TAKES A SUBSTANTIAL STORM TO DO THAT. SO LET'S INCREASE THE HEIGHT
AND STRENGTH OF THE WATER TO STORM LEVELS/HIGH RATE OF FLOW
.SAMPLINGSEDIMENTTREAMS
One of the primary methods
used in diamond exploration is
stream sediment sampling
designed to search for kimberlitic
indicator minerals. The indicator
minerals may be carried
downstream for hundreds of
miles.
PYROPE GARNETCHROMIAN DIOPSIDE
This is the classical kimberlitic indicator
minerals in the field. This mineral has an
average specific gravity of 3.4 thus it can be
readily captured in a gold pan with black
sand concentrates.
MEGACRYSTS ALSO PROVIDE A
GOOD SOURCE FOR
INDICATOR MINERALS
PERIDOTITE NODULE FROM
KIMBERLITE. NOTE THE ROUNDED
PYROPES IN THIS SPECIMEN
THE TRADITIONAL KIMBERLITIC INDICATOR MINERALS ARE RARE TO NON-EXISTENT
IN LAMPROITE THESE MINERALS MAY BE CONSIDERED UNFORTUNATELY HAVE LOW
SPECIFIC GRAVITY, POOR RESISTANCE TO ABRASION, AND ARE POTENTIALLY
DIFFICULT TO IDENTIFY. THE BETTER INDICATORS FOR DIAMONDIFEROUS
LAMPROITE HAVE BEEN DIAMOND, AND OLIVINE.
zircon Phlogopite