History & Introduction
Iolite gemstone is a transparent gem-quality form of cordierite, a composition of
magnesium iron aluminum cyclosilicate mineral. Even though the mineral has history
of dates back hundreds of years, the actual gemstone 'iolite' is considerably relatively
new and little known. The first significant and exciting discovery of large iolite
gem in transparent, gem-quality was made in 1996 in Palmer Creek, Wisconsin (USA)
by W. Dan Hausal, an American geologist. The largest iolite crystal in the world
was discovered south of Palmer Creek, in Grizzly Creek, Wisconsin and its weight
is above 24,000 carats.
The name 'iolite' comes from the Greek word 'ios' that means 'violet'. Iolite's
strong pleochroism received the misleading trade name of 'water-sapphire', a name
now obsolete. The view of the gemstone is as from one direction, appears sapphire-like
blue and from another appears as clean like water. Furthermore, from the top view
down, it appears light golden or honey-yellow in color. 'Dichroite' is another word
for iolite in reference to its pleochroic ability; 'dichroite' is a Greek word that
loosely means as 'two-colored rock'. Iolite gemstone is even famous for 'the Viking
stone' because according to Norse legend, Vikings used iolite as a polarizing filter
to help them find the sun on cloudy days.
Recognise - Gem-quality of iolite gemstone varies in color that
is from sapphire blue to violet-like blue and from light-blue to yellowish-gray.
The strong pleochroic characteristics is often used to identify and discern the
gemstone amongst other similar colored gemstones. At times iolite is mistaken for
sapphire and tanzanite, however it is softer as compared to sapphire, but harder
than tanzanite. Other gems that may even cause confusion that includes spinel and
garnet, however both spinel and garnet are refractive in a single manner that means
the iolite's trichroism is absent.
Availability - The deposits of iolite gemstone is found in numerous
locations around the world. Maximum iolite gemstones come from India, however there
are other significant sources too like Myanmar (Burma), Australia (Northern Territory),
Canada (Yellowknife), Brazil, Madagascar, Namibia, Sri Lanka (Ceylon), Tanzania
and the United States including Wyoming and Connecticut.
Buying Guide
Color - Naturally the iolite stone is in light to dark blue and
violet, though it is even available in various shades of green, yellow, brown or
gray. The maximum color in demand is an intense violet blue, which is the rival
of tanzanite. Iolite is trichroic that deals with three different colors, which
is seen in the same stone depending on the viewing angle. Few of the less grade
or poorly cut iolite appears overly dark or 'inky', gives a closer look to blackish.
Clarity and Lustre - The mineral cordierite is looks naturally
opaque, but fine gem-quality iolite looks like transparent to translucent in terms
of clarity. In many cases, the cutting quality of the gem affects the clarity. Stones
when are cut too deep appears to be opaque. Mainly the iolite shows few of the visible
inclusions, especially in larger stones. Though they are rarely seen, eye-clean
specimens are not unheard of. After it is polished, iolite displays an oily to vitreous
luster.
Cut and Shape - This gemstone is quite often step cut to enhance
color and to lighten the tone it is regularly intentionally 'windowed' or shallow
cut. Cutters must properly angle the rough seeing the iolite's trichroism of blue,
gray and near colorless forms. Mainly the common shapes for finished stones adds
up to traditional faceted rounds, pear and ovals shapes. Fancy shapes and calibrated
sizes are relatively accessible.
Treatment - For the case of iolite known treatments or enhancements
are there, though there is the availability of synthetic cordierite that is primarily
used for ceramics and other industrial purposes.
Gemological Characteristics: