(CNN)U.S. Supreme Court Justice Antonin Scalia has died at the age of 79, a government source and family friend told CNN on Saturday.

Scalia died in his sleep during a visit to Texas.

The first Italian-American to sit on the nation's highest court, Scalia was a conservative in thought, but not in personality.

The jaunty jurist was able to light up, or ignite, a room with his often brash demeanor and wicked sense of humor, grounded always in a profound respect for American law and its constitutional traditions.

"What can I say," was a favorite phrase of the man colleagues knew as "Nino." As it turned out, quite a lot.

"Justice Scalia had an irrepressibly pugnacious personality," said Edward Lazarus, a former Supreme Clerk law clerk who wrote about the experience in "Closed Chambers."

"And even in his early years of the Court, that came out at oral argument when he was the most aggressive questioner. And behind the scenes, where the memos he would write-- what were called 'Ninograms'-- inside the court had a real galvanizing effect on the debate among the justices."

A sharp mind combined with a sharp pen allowed Scalia to make his point, both to the pleasure and disappointment of his colleagues and the public.

"He could be belligerent, he was obviously very candid about he felt about things," said Joan Biskupic, a USA Today reporter who wrote a biography of Scalia. "He loved to call it as he saw it, completely not politically correct. In fact, he prided himself on not being PC on the bench in court."

His New York and Mediterranean roots -- "I'm an Italian from Queens" he was fond of saying-- helped fashion a love of words and debate, combining street smarts with a well-calculated conservative view of the law and its limits on society.

"He was very good with audiences that weren't predisposed to like him," said Paul Clement, a former Scalia law clerk. "He was incredibly disarming and charming in his own way."

Former CNN Supreme Court Correspondent Bill Mears researched and wrote much of this obituary prior to Justice Scalia's death. CNN's Steve Almasy and Kevin Bohn contributed to this report.