History & Introduction
For the creation of spring jewelry chalcedony is considered to be an excellent gemstone.
It is available in silky light-blue color and is delicate in nature, it reminds
of early morning mountain sky. Its name is said to come from an ancient Greek town
called Chalkedon, now in Turkey. This gemstone possess the property of fine-grained
variety of quartz with a luster that is waxy and microscopic compressed crystals.
Due to this structure, chalcedony is mainly semi-opaque that gives a soft glow when
the light diffuses through the stone. It is perfect for graceful jewelry.
The Romans used chalcedony to make seals and the stone is carved into ornaments
for ages. In the past its heavenly blue color give reason that why it was called
Mecca stone and St Stephen's stone.
Chalcedony comes from the quartz group of minerals. According to technical view
chalcedony is the gemological term applicable for every kinds of quartz in cryptocrystalline
form that occurs in a wide range of colors, sizes and patterns. Currently, the term,
'chalcedony', is maximum used in reference to a very specific type of cryptocrystalline
quartz, often referred to as 'actual chalcedony' or 'chalcedony in the narrow sense'.
Cryptocrystalline quartz is a compact to dense form of silica that shows it has
extremely fine crystallization. Indeed, maximum cryptocrystalline crystals are so
fine that it is not possible to see distinct particles under a microscope. Few of
the cryptocrystalline material are sub-classified as 'microcrystalline' that refers
to cryptocrystalline material with slightly larger crystals (discernable when sliced
thinly and observed under a polarizing microscope).
The real name 'chalcedony' originated from the latin word 'Chalcedonius' that is
thought to be derived from 'Chalcedon', an ancient seaport of Asia Minor, now Kadikoy,
Turkey. Chalcedony is famous to take a perfect polish, actually, after a prolonged
polish, some chalcedony varieties show a glow, which seems to emanate from within.
Recognise - Naturally, chalcedony quartz is identified from other
minerals because of its composition (silicon dioxide), superior hardness and hexagonal
crystal structure. Chalcedony is even known to possess slight piezoelectricity,
just like tourmaline that shows it can carry a small electrical charge. Unexpectedly,
as common as quartz is, there are actually some materials available that are easily
mistaken for chalcedony.
In fact discerning chalcedony quartz from other minerals is easily possible, recognizing
each varieties from within the chalcedony group is very difficult, as this needs
accurate observation of color, patterns, impurities and even the area. Another factor
that helps to identify chalcedonic varieties is even more difficult, it is with
many specimens that fall under multiple trade names.
Some of the most popular 'official' chalcedony varieties are-
Agate: Agate is differentiated with multiple colors. Some are available in solid
colors like green and black, however maximum stones available on the market currently
are dyed to obtain their color. 'Fire agate', other popular agates are jasper, geode,
dendritic, tree, Botswana, blue lace, fossil, iris, laguna, landscape, scenic, tube,
snakeskin, Sweetwater, Mohave blue, thunder egg, Fairburn, Dry head and Lake Superior.
Bloodstone: Bloodstone is opaque by nature, the chalcedony in dark-green color including
red to brown spotting.
Blue Chalcedony: The color is from grayish blue, ranging from light to medium color
intensity. Blue chalcedony comes from Namibia and is also called "African blue",
it ranges from grayish to nearly pure blue and from light to medium dark.
Onyx: Onyx is available in layers with a black base and a white upper layer. At
times uni-colored chalcedony is called onyx.
Carnelian: Carnelian gemstone is available in color from yellow-orange to rich,
near-reddish orange to orangey brown.
Chrysoprase: It is an apple-green chalcedony, which gets the color from nickel,
ranging from nearly opaque to transparent.
Chrysocolla chalcedony: This gemstone is one of the most valuable and rare varieties
of chalcedony. It is differentiated by its soft blue to blue-green color.
Petrified wood: Petrified wood (also called fossilized wood) is fossilized organic
remains that undergo a petrification process. Naturally, the organic remains are
replaced by chalcedony minerals that results in a very interesting and attractive
wood-like gemstone.
Availability - Chalcedony is a compact silica mainly it is found
in sedimentary or volcanic environments. Though, some regions are better known than
others, excellent quality chalcedony deposits are found across the globle. Almost
all of the United States is known to produce chalcedony. Besides for the lighter,
translucent and bluish 'actual chalcedony' material the sources are Uruguay, India,
Madagascar, Myanmar (Burma), Mexico, Brazil and Southwestern Africa.
Mentioned are the specific varieties of chalcedony availability:
Australia: Agate, chrysoprase, bloodstone
Brazil: Agate, chalcedony, bloodstone, chrysoprase
China: Agate, bloodstone
India: Agate, chalcedony, bloodstone, carnelian, chrysoprase
Kazakhstan: Chrysoprase
Madagascar: Agate, chalcedony, chrysoprase
Mexico: Agate
Mongolia: Agate
Namibia: Agate, blue chalcedony, chalcedony,
Russia: Chrysoprase
Sri Lanka: Chalcedony,
Uruguay: Agate, chalcedony,
South Africa: Chrysoprase
Tanzania: Chrysoprase
Zimbabwe: Chalcedony, chrysoprase
USA: Agate (Montana and Wyoming), chalcedony (California), chrysocolla, chalcedony,
petrified wood (Arizona), bloodstone, blue chalcedony (California, Nevada, Oregon).
Usages - If you design handcrafts, try making matching chalcedony
earrings and a bracelet. Small beads with subtle silver spacers for style. It is
sold in a white or light-blue box. It is accepted that chalcedony quartz is one
of the most significant materials of all time. It is not only used in jewelry industry,
however it is also an important material used for various scientific and industrial
uses as well.
Buying Guide
Color - Technically, chalcedony is referred to any translucent,
cryptocrystalline quartz along with a solo color, however in case of gem trade,
mainly it is used to refer for specimens with light bluish, white or gray color.
Commonly used colors for 'chalcedony in the narrow sense' is available in light
tan, blue-white, yellow, buff, gray or brown. Chalcedony gets color from the impurities
of quartz mainly it includes iron, titanium, nickel and copper. Chalcedony is available
every color, however in case of jewelry it's usually light milky blue with a hint
of pink. Due to porous nature, it is dyed blue and pale minty-green for centuries
- and at times its color improve to emerald green and even tangerine and peachy
pink.
Clarity and Lustre - Chalcedony appears to be translucent to opaque,
with translucent materials, which more in demand. It possess attractive luster once
it is cut and polished, maximum time it appears to be waxy or vitreous to dull.
In general, chalcedony is often milky with hidden color. The cloudy distribution
is a good indication of validity as long as the translucency remains unaffected,
the milky clarity does not significantly affect the overall value. Chalcedony mainly
shows visible inclusions that in maximum cases are considered acceptable.
Cut and Shape - Naturally, chalcedony is cut en cabochon. Cabochon
style cutting highlights the glow that is in demand and which it is prized too.
Rarely, very transparent materials are faceted. Maximum popular shapes available
are cushion, oval and round, however they are also commonly fashioned with fancy
shapes like flower-cuts, trillions and hearts. Drilled beads as well as tumbled
stones are very popular, particularly owing to the durability of chalcedony. Chalcedony
is an ideal material for gemstone carvings that adds up to ornamental figurines,
cameos, seals and insignia.
Treatment - Rarely, chalcedony is color-enhanced with dyeing. Irradiation
is not very common, but still in use. Chalcedony is heated, however heating will
maximum time yield reddish materials. Heating, dyeing and irradiation are not very
common for 'actual chalcedony', however they performed acted on different varieties
of chalcedony. Actual chalcedony is naturally left untreated and unenhanced totally
in production from the mine to the market. Chalcedony is actually quite porous that
allows it to be easily dyed to imitate various gems. In maximum cases, dyeing is
not done just to imitate different gem type like turquoise or howlite, but it is
done to replicate a particular variety of itself like carnelian or banded agate.
Including dyeing, some materials may have been bleached to help achieve desired
colors when dyeing.
Gemological Characteristics: