Pennsylvania Ballet opened its 50th anniversary season with a celebration of pure, luxurious beauty with the company premiere of George Balanchine's Jewels Thursday night at the Academy of Music.

It is a plotless ballet in three acts - "Emeralds," set to music by Faure; "Rubies" to Stravinsky; and "Diamonds" to Tchaikovsky - but the dancers conveyed bits of story.

Lauren Fadeley and Ian Hussey darted playfully through formations of corps dancers in puffs of green tulle while performing swirling arm movements, grand developees, and luscious port de bras. Their costumes glittered like gemstones, but their actions evoked new life blossoming from the earth.

Lillian De Piazza and Lorin Mathis took a more serious approach, with sharper movements and arms and legs seeming to tick off hours on a clock.

While "Emeralds" was beautiful, "Rubies" was breathtaking, with sharp hip motions, off-balance positions, long-legged prances en pointe, and deep stretches set to Stravinsky.

Amy Aldridge (a long-term principal) and Alexander Peters (a corps dancer who joined the company in 2012) don't seem an obvious pairing, but they clicked. Aldridge was a delight, with sharp, clean footwork, and Peters was a steady partner. Sometimes he pulled her into deep arabesques, other times they just marked the movement, shrugging whimsically in between.

Caralin Curcio was the unannounced replacement for an injured Gabriella Yudenich in a solo marked by impressive back attitude positions and statuesque poses.

The "Diamonds" section was every bit as opulent as its name suggests, opening with dancers in silvery-white costumes waltzing across the stage. Zachary Hench wooed an intentionally tentative Julie Diana in a very classical pas de deux they danced with delicate precision.

"Diamonds" concluded with a large cast promenading in lines across the stage, forming almost streams of glittery tennis bracelets, and intersecting into tiara shapes.

Diamonds, emeralds, and rubies, like a company marking 50 years, are rare and majestic, worthy of celebration. But this one was a little low-key. After a half-century, a piece d'occasion, the presentation of founder Barbara Weisberger, or a parade of past and present dancers would have been fitting.

Pennsylvania Ballet will repeat "Jewels" at 2 and 8 p.m. Oct. 26 and 2 p.m. Oct. 27 at the Academy of Music. $25-$135. 215-893-1999,