HELIOTROPE OR BLOODSTONE[GEM]
Listing
description
Heliotrope is a green variety of chalcedony, containing
red inclusions of iron oxide. These inclusions resemble drops of blood, giving heliotrope its alternative name of bloodstone.
A similar variety, in which the spots are yellow instead of red is known as plasma.
Detail
description
Heliotrope is a green variety of chalcedony, containing
red inclusions of iron oxide. These inclusions resemble drops of blood, giving heliotrope its alternative name of bloodstone.
A similar variety, in which the spots are yellow instead of red is known as plasma.
Chalcedony (pronounced /kælˈsɛdəni/) is a cryptocrystalline form of silica, composed of very fine intergrowths of the
minerals quartz and moganite.[2] These are both silica minerals, but they differ in that quartz has a
trigonal crystal structure, whilst moganite is
monoclinic. Chalcedony's standard Chemical
structure (Based on the
chemical structure of quartz) is SiO2 (Silicon Dioxide).
Chalcedony has a
waxy luster, and may be semitransparent or translucent. It can assume a wide
range of colors, but those most commonly seen are white to gray, grayish-blue
or a shade of brown ranging from pale to nearly black.
The name
"chalcedony" comes from Latin calcedonius, the word used to
translate the Greek word khalkedon, found only once, in the Book
of Revelation;
according to the OED a connection with the town of Chalcedon in Asia Minor is "very doubtful".[3] There is no reason to assume that the
precious stone referred to by this name in the Bible is the same as what is now
understood by the name.[4]
Varieties
Agate
Agate is a variety of chalcedony with
multi-colored curved or angular banding. Fire agate shows iridescent phenomena
on a brown background; iris agate shows exceptional iridescence when light
(especially pinpointed light) is shone through the stone. Landscape agate is
chalcedony with a number of different mineral impurities making the stone
resemble landscapes.[5]
Aventurine
Aventurine is a form of quartz, characterised by its translucency and the
presence of platy mineral inclusions that give a shimmering or glistening
effect termed aventurescence.
The most common
colour of aventurine is green, but it may also be orange, brown, yellow, blue,
or gray. Chrome-bearing fuchsite (a variety of muscovite mica) is the classic inclusion, and gives a
silvery green or blue sheen. Oranges and browns are attributed to hematite or goethite. Because aventurine is a rock, its physical properties vary: its specific gravity may lie between 2.64-2.69 and its hardness is somewhat lower than single-crystal
quartz at around 6.5.
Aventurine
feldspar or sunstone can be confused with orange and red
aventurine quartzite, although the former is generally of a higher
transparency. Aventurine is often banded and an overabundance of fuchsite may
render it opaque, in which case it may be mistaken for malachite at first glance.
The name aventurine
derives from the Italian "a ventura" meaning
"by chance". This is an allusion to the lucky discovery of aventurine
glass or goldstone at some point in the 18th century.
Although it was known first, goldstone is now a common imitation of aventurine
and sunstone. Goldstone is distinguished visually from the latter two minerals
by its coarse flecks of copper, dispersed within the glass in an
unnaturally uniform manner. It is usually a golden brown, but may also be found
in blue or green.
The majority of
green and blue-green aventurine originates in India (particularly in the vicinity of Mysore and Madras) where it is employed by prolific
artisans. Creamy white, gray and orange material is found in Chile, Spain and Russia. Most material is carved into beads and
figurines with only the finer examples fashioned into cabochons, later being set into jewellery.
Main markets for
aventurine are landscape stone, building stone, aquaria, monuments, and
jewellery.
Carnelian
Carnelian (also spelled cornelian) is a
clear-to-translucent reddish-brown variety of chalcedony. Its hue may vary from
a pale orange, to an intense almost-black coloration. Similar to carnelian is sard,
which is brown rather than red.
Chrysoprase
Chrysoprase
Chrysoprase (also spelled chrysophrase) is
a green variety of chalcedony, which has been colored by nickel
oxide. (The darker
varieties of chrysoprase are also referred to as prase. However, the
term prase is also used to describe green quartz, and to a certain extent is a
color-descriptor, rather than a rigorously defined mineral variety.)
Heliotrope
Heliotrope is a green variety of chalcedony,
containing red inclusions of iron oxide. These inclusions resemble drops of blood, giving heliotrope its alternative name of bloodstone.
A similar variety, in which the spots are yellow instead of red is known as plasma.
Moss agate
Moss
agate (also known as tree
agate or mocha stone) contains green filament-like inclusions,
giving it the superficial appearance of moss or blue cheese. It is not a true form of agate, as
it lacks agate's defining feature of concentric banding.
Mtorolite
Mtorolite is a green variety of chalcedony,
which has been colored by chromium. It is principally found in Zimbabwe.
Onyx
Onyx
Onyx is a variant of agate with black and
white banding. Similarly, agate with brown, orange, red and white banding is
known as sardonyx.
History
As early as the Bronze Age chalcedony was in use in the Mediterranean region; for example, on Minoan Crete at the Palace of Knossos, chalcedony seals have been recovered dating to circa
1800 BC.[6] People living along the Central Asian trade routes used various forms of
chalcedony, including carnelian, to carve intaglios, ring bezels (the upper faceted
portion of a gem projecting from the ring setting), and beads that show strong
Graeco-Roman influence.
Fine examples of
first century objects made from chalcedony, possibly Kushan, were found in recent years at Tillya-tepe in north-western Afghanistan.[7] Hot wax would not stick to it so it
was often used to make seal impressions. The term chalcedony is
derived from the name of the ancient Greek town Chalkedon in Asia Minor, in modern English usually spelled Chalcedon, today the Kadıköy district of Istanbul.
At least three
varieties of chalcedony were used in the Jewish High Priest's Breastplate.
(Moses' brother Aaron wore the Breastplate, with inscribed gems representing
the twelve tribes of Israel). The Breastplate included jasper, chrysoprase and
sardonyx, and there is some debate as to whether other agates were also used.
In the 19th
century Idar Oberstein became the world's largest chalcedony processing center,
in particular agates. Most of these agates were sourced in Latin America, in
particular Brazil. Originally the agate carving industry around Idar and
Oberstein was driven by local deposits that were mined in the 15th century. Several factors contributed to the
re-emerge
PRICE
$22/KG OR $10/IB
For more information:
mobile: +2348039721941
contact person: emeaba uche
e-mail: emeabau@yahoo.com
website: www.franchiseminerals.com
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