Buy Transparent Water Opal Gemstones Online
Water opal is opal reduced to its most elemental form — a stone so transparent, so free of
color, and so perfectly glassy that it appears to contain a suspended drop of pure water
within its body. Known across the trade by several names — hyalite opal, jelly opal, crystal
opal (in some contexts), and "opal agua" in Spanish — water opal shares opal's fundamental
chemistry (hydrated amorphous silica) but differs from other opal varieties in the one quality
most associated with opal: it may or may not display play of color. Water opal that displays
play of color within its colorless transparent body is extraordinary — the spectral flashes
appear to float suspended within a clear liquid, producing a visual effect unlike any other
gemstone. Water opal without play of color is valued for something equally distinctive:
its perfect, glassy, water-clear transparency and the way it interacts with light as a
colorless lens.
One of the most scientifically interesting features of water opal — particularly the hyalite
variety — is its fluorescence. Many hyalite opals display brilliant green fluorescence under
ultraviolet light, visible from across a room when the UV lamp is brought close. This green
UV glow is attributed to trace uranium content in some specimens, creating a stone that has
an entirely different visual identity under UV illumination than under visible light. Collectors
who enjoy UV-fluorescent minerals frequently prize hyalite opal for this striking property.
Types of Water Opal
Water opal encompasses several related but distinct transparent-to-translucent opal types
that share the quality of transparency or near-transparency as their defining characteristic.
Hyalite (also called Müller's Glass after Austrian mineralogist Franz-
Joseph Müller von Reichenstein, who first described it, or Waterstone) is a transparent
to translucent, colorless opal that typically forms in botryoidal (grape-like cluster)
shapes on the surfaces of volcanic rocks, pegmatites, and fumarole environments. The name
hyalite derives from the Greek "hialos" meaning glass — a perfect description of its
appearance. Hyalite shows little to no play of color but may display the striking green
UV fluorescence described above. It is found in Mexico, Poland, Czech Republic, Hungary,
Australia, and the USA.
Jelly opal is a trade name for transparent to translucent precious opal
with a gelatinous, slightly hazy appearance and subtle play of color. It ranks slightly
darker than crystal opal on the body tone scale. Fine jelly opal with good play of color
and clean transparency ranges from $5 to $140 per carat.
Girasol opal (from the Italian for sunflower) is a transparent to
semi-transparent opal that displays a subtle bluish or golden glow that follows the movement
of the light source — not play of color in the true Bragg diffraction sense but a subtle
adularescent-like effect from microscopic inclusions. Notable girasol sources include Mexico
and Oregon in the United States.
Contraluz opal is a rare variety that displays play of color in both
transmitted and reflected light — viewing the stone face-up shows one pattern; backlit,
the play of color transforms. Found primarily in Mexico, contraluz opal is one of the
rarest commercial opal types and commands premium collector pricing of $150 to $200 per
carat.
For comprehensive gemological information, read our
Water Opal Gemopedia Guide. Browse related opal
varieties including rainbow opal,
fire opal, and
yellow opal, with guides at
Rainbow Opal Guide,
Fire Opal Guide, and
Yellow Opal Guide.
See the complete Opal Gemstone Guide and browse our full
natural opal collection.
Water Opal Properties
Hardness: 5.5 to 6 Mohs
Refractive Index: approximately 1.37 to 1.47
Specific Gravity: 1.98 to 2.20
Transparency: Transparent to translucent — defining characteristic
Color: Colorless to faintly tinted; may show pale blue, golden, or greenish
tints from trace impurities
Play of Color: Present in jelly and contraluz types; absent or minimal in
pure hyalite
Fluorescence: Strong green under UV in many hyalite specimens — one of the
most vivid UV fluorescence responses of any natural gem
Treatment: Natural and untreated
Sources
Mexico (particularly Jalisco, Chihuahua, and San Luis Potosí states) is the primary source
of gem-quality water opal and hyalite. San Luis Potosí produces completely transparent,
colorless precious opal with play of color that is among the finest water opal available.
Ethiopia produces hydrophane crystal opals that cross into the water opal category when
transparency is high and body color is minimal. The USA (Oregon) produces girasol-type
water opal. Czech Republic, Poland, Hungary, and Brazil produce hyalite specimens primarily
for the mineral collector rather than the gem market.
Price and Value
Jelly opal and standard hyalite without significant play of color: $5 to $50 per carat.
Water opal with subtle play of color and good transparency: $30 to $200 per carat.
Fine precious water opal with vivid play of color suspended within a transparent colorless
body: $200 to $2,500 per carat for exceptional specimens. Contraluz opal: $150 to $200 per
carat. All water opal is entirely natural and untreated. Browse our complete
water opal collection or explore the
full natural opal gemstone range.
Frequently Asked Questions
What is water opal?
Water opal (also called hyalite, jelly opal, or crystal opal in some contexts) is a
transparent to translucent opal with a glassy, colorless or faintly tinted body. It is valued
for its clarity and glass-like transparency. Some water opals display play of color suspended
within the clear body; others (hyalite) are valued for their strong green UV fluorescence.
Mexico and Ethiopia are the primary sources.
Does water opal show play of color?
It depends on the type. Precious water opal (jelly opal) displays play of color within a
transparent body — an extraordinary appearance where spectral flashes appear to float in a
clear liquid. Hyalite typically shows no play of color but displays strong green UV
fluorescence. Contraluz opal shows play of color in both reflected and transmitted light.
What is hyalite opal?
Hyalite is a transparent, colorless opal forming in botryoidal (grape-like) clusters on
volcanic rock surfaces. Named from the Greek "hialos" meaning glass, it was first described
by Austrian mineralogist Franz-Joseph Müller von Reichenstein. Many hyalite specimens display
brilliant green fluorescence under UV light from trace uranium content. Found in Mexico,
Czech Republic, Poland, Hungary, Australia, and USA.
Is water opal the same as Ethiopian opal?
Not always. Ethiopian Welo opal is hydrophane (absorbs water) and is often transparent
with strong play of color — it overlaps with the water opal category when it is crystal-clear.
Water opal is a broader term for any transparent to translucent opal. All Ethiopian Welo opal
is hydrophane; most Mexican water opal is not. Mexican water opal is generally more stable.
How do I care for water opal?
Clean with warm water and a soft cloth only. Never use ultrasonic cleaners, steam cleaning,
or sudden heat. Avoid prolonged heat or direct sunlight. Store in moderate humidity. Mexican
water opal is relatively stable; Ethiopian hydrophane water opal requires additional care to
avoid rapid drying cycles that could cause crazing.
