Bona Mugabe, now 75, recalls that "there was an eclipse of the moon" the night she gave birth to her third child at a Catholic mission station in Zvimba tribal trust land. In the folklore of her people it was a sign that the new child was going to be great in the future.

Scientific records bear out Bona Mugabe's empirical observations. The "astronomical ephemerus" for 1924 lists an eclipse of the full moon the night of Feb. 20-21. That gave the white sphere a cinnamon hue visible in southern Africa. But it will have to be left to the as yet unwritten history books to verify the tribal interpretation of the lunar phenomenon that occurred when Robert Gabriel Mugabe was born.

For the time being, Zimbabwe's new prime minister, who was in New York Monday as his country became the United Nations' 153rd member and who will be seeking U.S. aid in a meeting today at the White House with President Carter, has captured center stage on the African continent. One of the few sefl-described Marxists ever popularly elected to office in the Third World, Robert Mugabe, 56, has embarked on an ambitious project to refreshion gradually but radically the second most industrialized country south of the Sahara, aiming to make it at the same time a showcase for economic development, nonalignment and tribal and racial harmony.

"If it's true he's a black Tito," said a white South African enthusiast of Mugabe, "then he's involved in a tremendously exciting experiment. It's the first time a [person with] Eurocommunist [views] has been given the levers of power in a Western-type economy." Hope is centered on Mugabe's credo of "Christian socialism" -- and, in the West, on his cool relations, to date, with the Soviet bloc.

"If it works, it'll be very infectious," and Alfred Knottenbelt, a teacher who supplied Mugabe with his books while he was in jail. "Very few African countries have realized quite the dreams they set out to."

Mugabe's nationalist credentials, his intellect, his breadth of knowledge and his vision of where he wants to go place him poles apart from Africa's Idi Amin, Emperor Bokassa and Sergeant Doe.

These qualities also suggest Mugabe may be destined to play to role beyond Zimbabwe's borders, in Third World politics and in "the democratization of South Africa," as Mugabe puts it. The Principle of Forgiveness

A strip of gray along Mugabe's hairline frames a shiny, ebony face that in repose appears impassive and severe. Often, when making a point in argument, he juts out his chin and closes his eyelids slowly in a haughty manner. At other times, as he listens or reads, the hint of a smile appears around his month as if he is sharing a joke with himself.

In his dress, Mugabe is both fastidious and fashionable. His suits ae sometimes accented with the flourish of a scarf thrown juantily around his neck and over one shoulder. That he places great store in proper attire was illustrated when he once ordered his maverick minister of manpower, Edgar Tekere (now involved in a controversial murder case), to leave a central committee party meeting and return with a jacket and the like everyone else. Tekere did as he was told.

Shy, reserved and professorial in demeanor, Mugabe does not appear at ease in front of groups. At one preelection rally when people began to leave in the middle of his remarks to be home by curfew hour, Mugabe was visibly angered and shouted, "Now you just sit down and listen." Few did.

In an attempt to influence the peasants in the countryside during the British-sponsored elections last February, the Rhodesian Air Force dropped pamphlets depicting Mugabe's face on the body of a lizard, his outstretched tongue grasping for a black child. "Mugabe, the dangerous chameleon," read the caption.

This is an assessment shared by Mugabe's foes and by many whites in Zimbabwe, among them some prominent former military leaders. His supporters would call it versatility. Whatever the adjective, it is an appraisal invited by Mugabe's own personality, which combines single-minded determination in pursuit of his goals with tactical flexibility.

It is this combination that has allowed Mugabe to endure 10 years of detention without trial under the former white minority government, survive the strife-ridden and assassination-riddled black political scene in Zimbabwe, lead a ruthless guerrilla war and return home after five years in exile "pledged to the principle of forgiveness."

His self-discipline means Mugabe keeps a tight rein on outward displays of emotion. "You never see Robert conspicuously reacting to anything. He's a very controlled person," said a former teacher. The Hostile Professor

As a child, the son of Gabriel Mugabe the carpenter "was always at the mission with his books, even during holidays," his how widowed mother told a newspaper.

High school principal David Garwe is a former schoolmate of Mugabe. He recalls him as a quiet person who did not mix well but who was good at memorizing poetry and doing traditional dances. He recalled once how when each child had to recite, "When I grow up to be a man, I want to be a . . . if I can," Mugabe said the wanted to be a professor.

After some years teaching in mission primary schools, Mugabe got a scholarship in 1949 to Fort Hare in Alice, South Africa. Here, at the first university for blacks in that part of the world, Mugabe came into contact with a generation of blacks fired with nationalist aspirations in the post-World War II "winds of change" breezing into Africa. It was here also that he was first introduced to the concept of Marxism; the South African Communist Party was not yet outlawed.

"The years there were the turning point in my career," Mugabe told one interviewer. "When I returned I was competely hostile to the system." Home again in 1952, he began teaching, eventually moving to northern Rhodesia, now Zambia, to take a post in a teacher's college.

But curiosity took him further afield, to the most interest ing African Country in 1957, Kwame Nkrumah's Ghana. There Mugabe soaked up Nkrumah's Pan-Africanist socialist philosphies and met Sarah "Sally" Hayfron, a Ghanaian schoolteacher and now his wife.

Back in Rhodesia in 1961, they were married in St. Peter's Catholic Church in the black township of Harare, outside Salisbury. But they have spent less than half of their married life together because of separations caused by Mugabe's political career.

Back home, the black educated class was chafing at its continued disenfranchisement under white rule. The young teacher, known for his brightness and now with the added aura of travel, was invited to enter politics. He joined the National Democratic Party, which later became the Zimbabwe African Peoples Union (ZAPU), led by Joshua Nkomo. But in 1963 Mugabe and others dissatisfied with Nkomo's direction broke away to form the Zimbabwe African National Union (ZANU). Rev. Ndabaningi Sithole became president, Mugabe secretary general.

But the Rhodesian authorities moved quickly and in 1964, as Mugabe got off a plane in Salisbury from a trip to Tanzania, he was arrested. He was not released until December 1974. The Fruits of Exile

Mugabe used his imprisonment to earn three degrees -- he already held two degrees from correspondence courses in addition to his Fort Hare diploma -- and further fulfill his childhood ambitions by teaching fellow detainees. Mugabe once told his wife that during those years "I lived with my books."

But he had a particularly painful experience when the government flatly refused to give him parole in 1966 to attend the funeral of his only child, a son who died at the age of 3 from encephalitis.

While in detention, Mugabe was elected to replace Sithole as head of ZANU by a group of top ZANU officials who also were jailed.

Three months after his release in 1974, the police came looking for Mugabe at his home. As they came down the front street, he was on his way down a back allley, recalls Bridget, the youngest of Mugabe's three surviving siblings. He and Tekere met at a prearranged place and then "driving, walkling and driving," according to his sister, they fled the country with police in pursuit. Once in Mozambique, they went to see Samora Machel, who had taken control of his country from the Portuguese in June that year. Machel's upport for ZANU'S guerrilla effort launched from Mozambique by Mugabe over the next five years has made him a fast and close friend. The Politics of Consensus

Mugabe's shift to flexibility, his preference for persuasion and consensus rather than coercion, his tendency to study and deliberate before making decisions and in some cases his indefinite postponment of decisions, such as appointing a replacement to retired high command chairman Lt. Gen.Peter Walls, have opended him to criticisms of being a weak leader.

A trait some people find difficult to understand is Mugabe's shrinking from retaliation and apparrent lack of grudges. None of the black leaders who opposed him during the war are in jail. Some men who threw a grenade at his home were released by police when Mugabe asked them to do so.

Since his return, Mugabe has never publicly mentioned his 10 years in detention without trial nor the fact that he was refused parole when his only son died. Whites have been welcomed as Zimbabwean citizens. A group of party dissidents who revelled against him during the war were not executed and are now free in Zimbabwe.

"It's this spirit in him I don't understand," said his sister Bridget. "When someone does bad to him, he doesn't hit back."

And yet, when tactics call for it, Mugabe can hit back. One Zimbabwean claims that he addressed a small, select group of blacks just before he left the country in 1975 and said that war was the only way to bring down the government even if it meant killing white men, women and children.

And despite his academic background, Mugabe can also play hardball as a politician. On a recent trip to Bulawayo, populated by members of the Matabele tribe who are followers of his main political foe, Joshua Nkomo, Mugabe confidently told the crowd that in Zimbabwe there must be "one country, one nation, one government and one cock," referring to the rooster that is his party's mascot. Meanwhile, Mugabe he sought to isolate Nkomo by giving his top lieutenants government jobs.

So far Mugabe has risen above complete identification with any one group, managing to be the benign conciliator. There may come a time when party unity requires him to be more dictatorial.

Mugabe's long years of study have proven to be his greatest asset.

"He is a genuine thinker," said an old friend. "He has thought out his values in life. He sees socialism as a method of solving the problem of uplifting the people." Courting the Capitalists

Philosophically, Mugabe says he finds no conflict between Christianity and socialism. "Socialism accept the brotherhood of man," he told an interviewer from South Africa televison. "It has humanitarianism built into it. It accepts that the resources of a country belong to the people as a whole and therefore must be exploited in the interest of the people as a whole. It rejects exploitation.

"I think those are also the principles of Christianity -- the common denominator of brotherhood running right through. As for the godless character of dialectical materialism, well, everyone knows there is always the right accept that or reject it, depending on whether they are atheistic or Christian in orientation,"he said.

"I've never believed personally the world has no origin. But of course, I do not believe there is a human god, some 'big man' in the form of a human being behind creatioin. But I believe there is some power behind creation and that therefore there is a God."

It's clear that Bon Mugabe's piety and the Jesuitical training Mugabe received at a Kutame mission have left a lasting influence on him.

These days, Mugabe, who does not smoke or drink, starts his days with some exercises and a bit of jogging before traveling to his office in a Mercedes flanked by four cars of bodyguards, both black and white. After receiving a daily briefing from the ministries of information and foreign affairs on world events in the previous 24 hours, Mugabe proceeds to get on with his task of rebuilding Zimbabwe, a process that is so far as fascinating to watch as an eclipse of the moon.