Skip to main content

Color Change Star Sapphire

GIA Certified 7.6 Carat Color Change Star Sapphire & Diamond 14K Gold Men's Ring
GIA Certified 7.6 Carat Color Change Star Sapphire & Diamond 14K Gold Men's Ring

GIA Certified 7.6 Carat Color Change Star Sapphire & Diamond 14K Gold Men's Ring

Located in Miami, FL

GIA Certified 7.60 carat no heat color change star sapphire bezel set men's ring in 14K solid

Category

21st Century and Contemporary Modern Fashion Rings

Materials

Diamond, Purple Sapphire, Gold, 14k Gold, Yellow Gold

Platinum AGL 15.79ctw No Heat Color Change Star Sapphire w/ Diamond Halo Ring
Platinum AGL 15.79ctw No Heat Color Change Star Sapphire w/ Diamond Halo Ring

Platinum AGL 15.79ctw No Heat Color Change Star Sapphire w/ Diamond Halo Ring

Located in Montclair, NJ

Mineral Type - Variety: Natural Corundum - Color - Change Star Sapphire Shape: Oval Cutting Style: Double

Category

21st Century and Contemporary Cocktail Rings

Materials

Diamond, Sapphire, Star Sapphire, Platinum

10.50 Carat Color-Change Star Sapphire Diamond Platinum Ring
10.50 Carat Color-Change Star Sapphire Diamond Platinum Ring

10.50 Carat Color-Change Star Sapphire Diamond Platinum Ring

Located in Beverly Hills, CA

A fine and rare sapphire exhibiting two phenomena, color-change and asterism (star-effect)! The

Category

21st Century and Contemporary American Fashion Rings

Materials

Diamond, Star Sapphire, Platinum

20.38 Carat Color-Change Star Sapphire Diamond Platinum Ring
20.38 Carat Color-Change Star Sapphire Diamond Platinum Ring

20.38 Carat Color-Change Star Sapphire Diamond Platinum Ring

Located in Beverly Hills, CA

A unique and special gem! It is a large 20.38 carat star sapphire which also has color change, two

Category

21st Century and Contemporary American Fashion Rings

Materials

Diamond, Star Sapphire, Platinum

Platinum No Heat Color Change Star Sapphire w/ Baguette Diamond Ring
Platinum No Heat Color Change Star Sapphire w/ Baguette Diamond Ring

Platinum No Heat Color Change Star Sapphire w/ Baguette Diamond Ring

Located in Montclair, NJ

--Stone(s):-- (1) Natural Genuine Star Sapphire - Oval Double Cabochon Cut - Prong Set - Color

Category

20th Century Cocktail Rings

Materials

Diamond, Sapphire, Platinum

Art Deco 8.08ct Star Sapphire Ring
Art Deco 8.08ct Star Sapphire Ring

Art Deco 8.08ct Star Sapphire Ring

Located in Litchfield, CT

: Ring size 7 WEIGHT: 7.2 grams STONES: 8.08 carat no-heat, Ceylon, color change, star sapphire

Category

Vintage 1920s American Cocktail Rings

Materials

Diamond, Star Sapphire, 18k Gold

Plum Pink Star Sapphire Ring 16 CT! Diamond Halo! *Moviestar Quality*
Plum Pink Star Sapphire Ring 16 CT! Diamond Halo! *Moviestar Quality*

Plum Pink Star Sapphire Ring 16 CT! Diamond Halo! *Moviestar Quality*

Located in Galveston, TX

*HUGE* 16.56 CARAT NATURAL COLOR-CHANGE PINK - PLUM STAR SAPPHIRE WITH 6 RAYS - VALENTINE'S DAY

Category

21st Century and Contemporary Hong Kong Contemporary Cocktail Rings

Materials

Diamond, Star Sapphire, 18k Gold, Platinum

Recent Sales

GIA Certified 18 Karat Gold and 21.36 Carat Purple Color Changing Star Sapphire
GIA Certified 18 Karat Gold and 21.36 Carat Purple Color Changing Star Sapphire

GIA Certified 18 Karat Gold and 21.36 Carat Purple Color Changing Star Sapphire

Located in West Palm Beach, FL

An elegant, 18kt yellow gold ring with a beautiful 21.36ct purple star sapphire. In, a beautiful

Category

21st Century and Contemporary Dome Rings

Materials

Star Sapphire, 18k Gold, Yellow Gold

Art Deco 25 Carat GIA Cert No Heat Color Change Star Sapphire Platinum Ring
Art Deco 25 Carat GIA Cert No Heat Color Change Star Sapphire Platinum Ring

Art Deco 25 Carat GIA Cert No Heat Color Change Star Sapphire Platinum Ring

Located in Carmel-by-the-Sea, CA

sapphire displaying a distinctive asterism and unique blue-to-purple color change. It¹s absolutely

Category

21st Century and Contemporary Engagement Rings

Materials

Diamond, Emerald, Sapphire, Platinum

Vintage GIA 8.73 Carat Cabochon Star Sapphire Diamond Platinum Ring
Vintage GIA 8.73 Carat Cabochon Star Sapphire Diamond Platinum Ring

Vintage GIA 8.73 Carat Cabochon Star Sapphire Diamond Platinum Ring

Located in Beverly Hills, CA

One Vintage GIA 8.73 Carat No Heat Ceylon Color Change Star Sapphire Diamond Platinum Ring

Category

Vintage 1970s Unknown Three-Stone Rings

Materials

Diamond, Star Sapphire, Platinum

18K Gold & Platinum 95.53ctw AGL Star Sapphire & Diamond Brushed Flower Pendant
18K Gold & Platinum 95.53ctw AGL Star Sapphire & Diamond Brushed Flower Pendant

18K Gold & Platinum 95.53ctw AGL Star Sapphire & Diamond Brushed Flower Pendant

Located in Montclair, NJ

- Change Star Sapphire Geographic Origin: Ceylon (Sri Lanka) Treatment: No gemological evidence of heat

Category

21st Century and Contemporary Pendant Necklaces

Materials

Diamond, Star Sapphire, 18k Gold, Platinum

19.03Ct Color-changing Violet Star Sapphire and Diamond in 18K White Gold
19.03Ct Color-changing Violet Star Sapphire and Diamond in 18K White Gold

19.03Ct Color-changing Violet Star Sapphire and Diamond in 18K White Gold

Located in Hong Kong, HK

exquisite piece lies a captivating 19.03-carat violet Star Sapphire. This particular gem is renowned for its

Category

21st Century and Contemporary Hong Kong Contemporary Cocktail Rings

Materials

Diamond, Star Sapphire, 18k Gold, White Gold

Amazing Color-Change Star Sapphire cts 4.51 'Lavender to Pink' Ring in 18k Gold
Amazing Color-Change Star Sapphire cts 4.51 'Lavender to Pink' Ring in 18k Gold

Amazing Color-Change Star Sapphire cts 4.51 'Lavender to Pink' Ring in 18k Gold

Located in Hong Kong, HK

Amazing color-change star sapphire cts 4.51 (Lavender to Pink) ring in 18 K gold. (Stock code

Category

21st Century and Contemporary Hong Kong Contemporary Engagement Rings

Materials

Star Sapphire, Diamond, Gold, White Gold

GRS Certified 45.63 Carat Untreated Star Sapphire Diamond Ring
GRS Certified 45.63 Carat Untreated Star Sapphire Diamond Ring

GRS Certified 45.63 Carat Untreated Star Sapphire Diamond Ring

Located in Hong Kong, HK

color changing star sapphire color range from violetish-blue (day light) to purple (incandescent light

Category

21st Century and Contemporary Hong Kong Modern Dome Rings

Materials

Diamond, Star Sapphire, 18k Gold

Gump's Jade Necklace, circa 1960s
Gump's Jade Necklace, circa 1960s

Gump's Jade Necklace, circa 1960s

By Gump's San Francisco

Located in Northampton, MA

change? It's not like color-change Alexandrite, a star sapphire or a chrysoberyl cat's eye? But jade does

Category

Mid-20th Century Chinese Modern Beaded Necklaces

Materials

Jade, 14k Gold

11, 04 Carat Natural Color Change Blue Purple Sri Lankan Sapphire
11, 04 Carat Natural Color Change Blue Purple Sri Lankan Sapphire

11, 04 Carat Natural Color Change Blue Purple Sri Lankan Sapphire

By D and A Style

Located in Singapore, SG

in sapphires. Perfect phenomenal Srilankan sapphire with perfect color change is something special

Category

21st Century and Contemporary Armenian Modern Dome Rings

Materials

Sapphire, Star Sapphire, Purple Sapphire, Gold, 18k Gold, Rose Gold, Whi...

Art Deco 5.54 Ct Natural No Heat Ceylon Sapphire Tiffany & Co. Platinum Unisex R
Art Deco 5.54 Ct Natural No Heat Ceylon Sapphire Tiffany & Co. Platinum Unisex R

Art Deco 5.54 Ct Natural No Heat Ceylon Sapphire Tiffany & Co. Platinum Unisex R

By Tiffany & Co.

Located in Napoli, IT

unheated color change star sapphire of 5.54 Ct (9.5 x 7.5 mm.)(GCS UK Certified) UK size: R 3/4 US size: 9

Category

Vintage 1930s Art Deco Solitaire Rings

Materials

Diamond, Sapphire, Platinum

People Also Browsed

Antique Ring 25ct natural Blue Sapphire solid 18K Gold Ø 4.75 US /9.6gr
Antique Ring 25ct natural Blue Sapphire solid 18K Gold Ø 4.75 US /9.6gr

Antique Ring 25ct natural Blue Sapphire solid 18K Gold Ø 4.75 US /9.6gr

Located in SE

Luxurious Antique Ring in Renaissance style, band and crown tested solid 18K Gold,not hallmarked, European, ca. XVIII - early XIX centuries. Huge cabochon of natural Light - Blue Sa...

Category

Antique Early 19th Century European Baroque Revival Solitaire Rings

Materials

Blue Sapphire, 18k Gold

14K Yellow Gold Burma Cabochon Ruby and Diamond Bezel Set Stud Earrings
14K Yellow Gold Burma Cabochon Ruby and Diamond Bezel Set Stud Earrings

14K Yellow Gold Burma Cabochon Ruby and Diamond Bezel Set Stud Earrings

By OGI Ltd

Located in New York, NY

A Timeless Expression of Elegance and Craftsmanship Step into a world of exquisite luxury with these 14K Yellow Gold Burma Cabochon Ruby and Diamond Stud Earrings. Each element—caref...

Category

2010s American Contemporary Stud Earrings

Materials

Diamond, Ruby, Gold, 14k Gold, Yellow Gold

Mens Diamond Ring 14K Gold Band .75ct Old European Solitaire Vintage
Mens Diamond Ring 14K Gold Band .75ct Old European Solitaire Vintage

Mens Diamond Ring 14K Gold Band .75ct Old European Solitaire Vintage

By Estate Jewelry

Located in East Brunswick, NJ

This amazing vintage ring is finely crafted in solid 14K Yellow Gold and set with a solitaire Old European cut diamond. The diamond is .75 carat of very clean VVS2 clarity and H col...

Category

20th Century Band Rings

Materials

Diamond, 14k Gold, Yellow Gold

Platinum Estate 3.00 Carat Star Sapphire and Diamond Ring
Platinum Estate 3.00 Carat Star Sapphire and Diamond Ring

Platinum Estate 3.00 Carat Star Sapphire and Diamond Ring

Located in Scottsdale, AZ

Platinum estate 3.00 carat star sapphire and diamond ring. Centering one oval star sapphire, four prong set, weighing approximately 3.00 carats. The sapphire features a six rayed sta...

Category

20th Century Art Deco Fashion Rings

Materials

Diamond, Star Sapphire, Platinum

Certified 3.05 Carat No Heat Purple Sapphire Diamond Gold Heart Ring
Certified 3.05 Carat No Heat Purple Sapphire Diamond Gold Heart Ring

Certified 3.05 Carat No Heat Purple Sapphire Diamond Gold Heart Ring

By Diamond Stars Jewelry, Inc.

Located in New York, NY

Very Unusual Sapphire Ring The ring is 18K White Gold It has 1.71 Carat in Diamonds F VS The Sapphire is 3.05 Carats Natural Purple NO Heat. The Sapphire is certified by LAPIS. The r...

Category

21st Century and Contemporary American Modern Engagement Rings

Materials

Diamond, White Diamond, Sapphire, Purple Sapphire, Gold, 18k Gold, White...

Portuguese Romantic Era  (1830-188) Rose cut Diamond Men Ring
Portuguese Romantic Era  (1830-188) Rose cut Diamond Men Ring

Portuguese Romantic Era (1830-188) Rose cut Diamond Men Ring

Located in OVIEDO, AS

Early Victorian Era Rose cut Diamond Men Ring (1837-1860) Antique Victorian Era Diamond Men’s Ring. Portuguese origin. The 18K/19K yellow gold (touchstone tested) ring is centered w...

Category

Antique Mid-19th Century Portuguese Romantic Solitaire Rings

Materials

Diamond, 18k Gold

Steven Battelle 12.6 Carats Rainbow Moonstone 22K Gold Ring
Steven Battelle 12.6 Carats Rainbow Moonstone 22K Gold Ring

Steven Battelle 12.6 Carats Rainbow Moonstone 22K Gold Ring

By Steven Battelle

Located in Soquel, CA

A luminous and flashing 12 mm high-dome cushion shaped cabochon rainbow moonstone rests in a vertical "4-point with jawan" Steven Battelle designed setting atop a tapered matte-finis...

Category

21st Century and Contemporary Balinese Contemporary Cocktail Rings

Materials

Rainbow Moonstone, Moonstone, 22k Gold

Ancient Greek 4th Century BC Eagle Coin 18K Gold Mens Ring
Ancient Greek 4th Century BC Eagle Coin 18K Gold Mens Ring

Ancient Greek 4th Century BC Eagle Coin 18K Gold Mens Ring

By Steven Battelle

Located in Soquel, CA

A clear and crisply struck image of an eagle carrying a snake in its talons is depicted on an authentic ancient Greek silver "drachm" coin struck in the seaport city of Chalkis on th...

Category

21st Century and Contemporary Balinese Classical Greek Cocktail Rings

Materials

18k Gold

GIA Certified 8.50 Ct Round Cut Fancy Color Diamond Men's Ring
GIA Certified 8.50 Ct Round Cut Fancy Color Diamond Men's Ring

GIA Certified 8.50 Ct Round Cut Fancy Color Diamond Men's Ring

Located in New York, NY

GIA Certified 8.50 ct Round Cut Fancy Color Diamond Solitaire Men's Ring 8.50 fancy yellowish brown round cut center diamond set in 18k gold hexagon motif band. Ring Size: 5.75 R...

Category

2010s American Solitaire Rings

Materials

Diamond, 18k Gold

CARTIER Paris Art Deco Enameled Cocktail Ring 18Kt Gold With Diamonds & Gemstone
CARTIER Paris Art Deco Enameled Cocktail Ring 18Kt Gold With Diamonds & Gemstone

CARTIER Paris Art Deco Enameled Cocktail Ring 18Kt Gold With Diamonds & Gemstone

By Cartier

Located in Miami, FL

An art deco ring designed by Cartier. This is a magnificent art deco ring, created in Paris France and designed by the jewelry house of Cartier. This colorful cocktail ring is very ...

Category

Vintage 1920s French Art Deco Cocktail Rings

Materials

Amethyst, Diamond, Jade, White Diamond, Gold, Yellow Gold, Enamel, 18k Gold

1.7 Carat, 7 Diamonds Traditional Men's Ring 14 Karat Yellow Gold Ring Estate
1.7 Carat, 7 Diamonds Traditional Men's Ring 14 Karat Yellow Gold Ring Estate

1.7 Carat, 7 Diamonds Traditional Men's Ring 14 Karat Yellow Gold Ring Estate

Located in New York, NY

1.7 Carat 7 Diamonds Traditional Men's Ring 14 Karat Yellow Gold Ring Estate This is a Nice traditional 7 diamond ring from our premium wedding collection for Men 7 Round dia...

Category

Early 2000s Wedding Rings

Materials

Diamond, 14k Gold

Heart garnet Eternity Ring in 14k gold
Heart garnet Eternity Ring in 14k gold

Heart garnet Eternity Ring in 14k gold

By Daizy Jewellery

Located in Istanbul, TR

14k gold ring with heart natural garnets. Heart garnet eternity ring band. Valentines gift jewelry. Full circle of hearts. January birthstone ring. Heart Garnet gold ring. Love ring....

Category

2010s Turkish Modern Bridal Rings

Materials

Garnet, 14k Gold

Magic Glo 1.56 Carat Diamond Halo Yellow Gold Men's Ring
Magic Glo 1.56 Carat Diamond Halo Yellow Gold Men's Ring

Magic Glo 1.56 Carat Diamond Halo Yellow Gold Men's Ring

Located in Stamford, CT

Bold and masculine Magic Glo men's square top diamond ring. 1 round brilliant cut center diamond set in a 14k yellow gold setting with 16 round brilliant cut accent diamonds in the f...

Category

Late 20th Century Fashion Rings

Materials

Diamond, Gold, 14k Gold, Yellow Gold

GIA Certified 1.02 Carat Natural Round Diamond Solitaire Mens Ring 14 Karat
GIA Certified 1.02 Carat Natural Round Diamond Solitaire Mens Ring 14 Karat

GIA Certified 1.02 Carat Natural Round Diamond Solitaire Mens Ring 14 Karat

Located in New York, NY

GIA certified 1.02 carat solitaire diamond ring. Report number 6213187765 Stating I color SI2 clarity & good cut. No fluorescence. Mounted in solitaire form 14kt 7.7 g Size 9.5...

Category

2010s American Solitaire Rings

Materials

Diamond, 14k Gold, Yellow Gold

Men's Diamond Yellow Gold Ring
Men's Diamond Yellow Gold Ring

Men's Diamond Yellow Gold Ring

Located in Geneva, CH

Men's ring in 18kt yellow gold set with 111 diamonds 1.70 cts and 16 square diamonds 1.40 cts and one diamond 0.60 Size 54

Category

21st Century and Contemporary Swiss Contemporary Fashion Rings

Materials

Diamond, 18k Gold, Yellow Gold

Big powerful men ring with rhodolith
Big powerful men ring with rhodolith

Big powerful men ring with rhodolith

Located in Berlin, BE

Introducing the majestic and powerful men's ring adorned with a commanding rhodolith in an oval cut. This remarkable ring is not for the faint of heart—it exudes strength and asserts...

Category

Early 2000s German Aesthetic Movement Fashion Rings

Materials

Amethyst, Gold, 14k Gold, Yellow Gold

Get Updated with New Arrivals
Save "Color Change Star Sapphire", and we’ll notify you when there are new listings in this category.

Color Change Star Sapphire For Sale on 1stDibs

You are likely to find exactly the color change star sapphire you’re looking for on 1stDibs, as there is a broad range for sale. Each design created in this style — which was crafted with great care and often made from gold, 14k gold and platinum — can elevate any look. Our collection of these items for sale includes 6 vintage editions and 29 modern creations to choose from as well. You’re likely to find the perfect color change star sapphire among the distinctive items we have available, which includes versions made as long ago as the 20th Century as well as those produced as recently as the 21st Century. Creating a color change star sapphire has been a part of the legacy of many jewelers, but those produced by Emilio!, Five Star Jewelry and D and A Style are consistently popular. Take a look at a color change star sapphire featuring diamond from our inventory today to add the perfect touch to your look. A brilliant cut version of this piece has appeal, but there are also cabochon and round cut versions for sale. When shopping for a color change star sapphire, you’ll find that there are less available pieces for unisex or men today than there are for women.

How Much is a Color Change Star Sapphire?

Prices for a color change star sapphire can differ depending upon size, time period and other attributes — at 1stDibs, these accessories begin at $390 and can go as high as $140,000, while this accessory, on average, fetches $9,015.

The Legacy of Sapphire in Jewelry Design

On 1stDibs, shop the bright blue gems that star in sapphire rings, sapphire necklaces and other vintage and antique sapphire jewelry

Sapphires — the stone of choice for Napoleon, Princess Diana and Elizabeth Taylor — have been a favorite of aristocrats and the well-to-do since the time of the Ancient Greeks.

Picture a sapphire. If the stone you conjure is a deep cornflower blue, you’re seeing only part of the picture. Although blue Kashmirs are considered the most valuable, sapphires come in every color except red. No matter the hue, this very special gem is rich in history and beloved by royals (FYI, Princess Diana and Kate Middleton share an 11-carat sapphire engagement ring), so September babies are in very noble company.

America’s version of royalty — old money and celebrities — have also shown a predilection for the blue stones. In 1940, John D. Rockefeller Jr. had Cartier mount a 62-carat sapphire he had bought from an Indian maharajah in a brooch for his first wife, Abby Aldrich Rockefeller; in 2001, the piece sold for a then-record of $3,031,000 at Christie’s New York.

The grand dame of jewelry, Elizabeth Taylor had a passion for the gems that her lovers were happy to indulge. Second husband Michael Wilding gave her an engagement ring set with a cabochon sapphire, while Richard Burton famously presented her with a BVLGARI sautoir set with diamonds and sapphires, including at its center a cabochon Burmese weighing 52.72 carats. One of the star lots in the sale of Taylor’s jewels at the Christie’s New York in 2011, it sold for $5,906,500.

You don’t have to have blue blood or a bulging bank account, however, to get an eyeful of this much-coveted gem. A number of outstanding examples reside in public collections.

The Smithsonian Museum of Natural History owns the 423-carat Logan sapphire, a gift from the Guggenheim family, and the Hall sapphire and diamond necklace, designed by Harry Winston and featuring 36 fine, well-matched cushion-cut Sri Lankan sapphires weighing a combined 195 carats. Also in the collection is the Bismarck sapphire necklace, designed by Cartier and sporting a central sapphire weighing 98.6 carats, which Mona Von Bismarck donated to the museum.

Sapphires are composed of corundum. Their color derives from trace elements, such as iron, titanium, chromium, copper or magnesium. When the trace element produces a ruby hue, the stone is called, what else, a ruby. (which is, as mentioned above, why sapphires cannot be red by definition).

The allure of large gemstones endures throughout the periods characterized as vintage, and sapphire features frequently in vintage engagement rings. (On 1stDibs, a range of buying guides can be found for those in the market for antique engagement ringsvintage engagement rings or Art Deco engagement rings.)  

Find an exquisite collection of vintage and antique sapphire jewelry on 1stDibs.

Finding the Right Rings for You

Antique and vintage rings have long held a special place in the hearts of fine jewelry lovers all over the world.

No matter their origin or specific characteristics, rings are timeless, versatile accessories. They’ve carried deep meaning since at least the Middle Ages, when diamond rings symbolized strength and other kinds of rings were worn to signify romantic feelings or to denote an affiliation with a religious order. Rings have also forever been emblematic of eternity.

Over time, rings have frequently taken the form of serpents, which have long been associated with eternal life, health and renewal. Italian luxury jewelry house Bulgari has become famous for its widely loved Serpenti motif, for example, and its Serpenti ring, like the other accessories in the collection, began as an homage to jewelry of the Roman and Hellenistic eras. The serpent is now a popular motif in fine jewelry. Jewelry devotees have long pined for rings adorned with reptiles, thanks to antique Victorian rings — well, specifically, Queen Victoria’s illustrious engagement ring, which took the form of a gold snake set with rubies, diamonds and an emerald (her birthstone). Designs for Victorian-era engagement rings often featured repoussé work and chasing, in which patterns are hammered into the metal.

Engagement rings, which are reliably intimidating to shop for, are still widely recognized as symbols of love and commitment. On 1stDibs, a range of buying guides can be found for those in the market for antique engagement ringsvintage engagement rings or Art Deco engagement rings

The most collectible antique engagement rings and vintage engagement rings are those from the Victorian, Edwardian and Art Deco eras. Named for the monarchies of the four King Georges, who in succession ruled England starting in 1714 (plus King William’s reign), antique Georgian rings, be they engagement rings or otherwise, are also coveted by collectors. Pearls, along with colored gemstones like garnets, rubies and sapphires, were widely used in Georgian jewelry. The late-1700s paste jewelry was a predecessor to what we now call fashion or costume jewelry

The Art Nouveau movement (1880–1910) brought with it rings inspired by the natural world. Antique Art Nouveau rings might feature depictions of winged insects and fauna as well as women, who were simultaneously eroticized and romanticized, frequently with long flowing hair. Art Deco jewelry, on the other hand, which originated during the 1920s and ’30s, is by and large “white jewelry.” White metals, primarily platinum, were favored over yellow gold in the design of antique Art Deco rings and other accessories as well as geometric motifs, with women drawn to the era’s dazzling cocktail rings in particular.

Whether you’re hunting down a chunky classic for a Prohibition-themed cocktail party or seeking a clean contemporary design to complement your casual ensemble, find an exquisite collection of antique, new and vintage rings on 1stDibs.