This particular apparition is new to me. Rather than try to cipher through it all right now, I'll paste the article from the Catholic Encyclopedia.
Located in the commune and parish of La Salette-Fallavaux, Canton of Corps, Department of Isere, and Diocese of Grenoble. It is celebrated as the place where, it is said, the Blessed Virgin appeared to two little shepherds; and each year is visited by a large number of pilgrims.
On 19 September, 1846, about three o'clock in the afternoon in full sunlight, on a mountain about 5918 feet high and about three miles distant from the village of La Salette-Fallavaux, it is related that two children, a shepherdess of fifteen named Mélanie Calvat, called Mathieu, and a shepherd-boy of eleven named Maximin Giraud, both of them very ignorant, beheld in a resplendent light a "beautiful lady" clad in a strange costume.
Speaking alternately in French and in patois, she charged them with a message which they were "to deliver to all her people". After complaining of the impiety of Christians, and threatening them with dreadful chastisements in case they should persevere in evil, she promised them the Divine mercy if they would amend.
Finally, it is alleged, before disappearing she communicated to each of the children a special secret. The sensation caused by the recital of Mélanie and Maximin was profound, and gave rise to several investigations and reports. Mgr. Philibert de Bruillard, Bishop of Grenoble, appointed a commission to examine judicially this marvellous event; the commission concluded that the reality of the apparition should be admitted.
Soon several miraculous cures took place on the mountain of La Salette, and pilgrimages to the place were begun. The miracle, needless to say, was ridiculed by free-thinkers, but it was also questioned among the faithful, and especially by ecclesiastics. There arose against it in the Dioceses of Grenoble and Lyons a violent opposition, aggravated by what is known as the incident of Ars.
As a result of this hostility and the consequent agitation, Mgr. de Bruillard (16 November 1851) declared the apparition of the Blessed Virgin as certain, and authorized the cult of Our Lady of La Salette. This act subdued, but did not suppress, the opposition, whose leaders, profiting by the succession in 1852 of a new bishop, Mgr. Ginoulhiac, to Mgr. Bruillard, who had resigned, retaliated with violent attacks on the reality of the miracle of La Salette. They even asserted that the "beautiful lady" was a young woman named Lamerliere, which story gave rise to a widely advertised suit for slander.
Despite these hostile acts, the first stone of a great church was solemnly laid on the mount of La Salette, 25 May, 1852, amid a large assembly of the faithful. This Church, later elevated to the rank of a basilica, was served by a body of a religious called Missionaries of La Salette. In 1891 diocesan priests replaced these missionaries, driven into exile by persecuting laws.
As said above, the Blessed Virgin confided to each of the two children a special secret. These two secrets, which neither Mélanie or Maximin ever made known to each other, were sent by them in 1851 to Pius IX on the advice of Mgr. de Bruillard. It is unknown what impressions these mysterious revelations made on the pope, for on this point there were two versions diametrically opposed to each other.
Maximin's secret is not known, for it was never published. Mélanie's was inserted in its entirety in brochure which she herself had printed in 1879 at Lecce, Italy, with the approval of the bishop of that town. A lively controversy followed as to whether the secret published in 1879 was identical with that communicated to Pius IX in 1851, or in its second form it was not merely a work of the imagination. The latter was the opinion of wise and prudent persons, who were persuaded that a distinction must be made between the two Mélanies, between the innocent and simple voyante of 1846 and the visionary of 1879, whose mind had been disturbed by reading apocalyptic books and the lives of illuminati.
As Rome uttered no decision the strife was prolonged between the disputants. Most of the defenders of the text of 1879 suffered censure from their bishops. Maximin Giraud, after an unhappy and wandering life, returned to Corps, his native village, and died there a holy death (1 March, 1875). Mélanie Calvat ended a no less wandering life at Altamura, Italy (15 December, 1904).