Mrs Matilda Charlotte Fraser Houstoun (1815?-1892), in her book "Hesperos, or Travels in the West", 1850, London, observed a young lady on board ship, who was returning from a Parisian convent school (to New Orleans?) and engaged her in conversation. The girl was a quadroon. The encounter is movingly described, and Mrs Houstoun wrote a poem about her.

This extract gives a feel for the times, and the treatment accorded persons of mixed race, regardless of their education and culture. Although on line, I think it worthwhile to quote here.

"As we left Halifax, I became greatly interested in one of our companions, who, having remained, during all the early part of the voyage, closely confined to her stateroom, made her appearance on deck shortly before her arrival at that place. She was very young and beautiful. Her dress was in the best possible taste, with Parisian grace lurking in every fold of her garments. Her hair, which was rich and luxuriant, was of a golden brown and dressed in the simplest style, but glossy and neat as that of one of Stearne's 'grisettes.' There was a look almost of high breeding in her small hands, and her manner was French and graceful in the extreme. This fair creature entered the saloon alone, and alone she remained, for lovely as she was, no one addressed her, but on the contrary, she appeared to be purposely avoided by everyone present. Even the commonest acts of civility were, in her case, neglected, and that by the very men who were generally foremost in paying attentions to the ladies who honoured the saloon by their presence. Seeing her in this deserted situation, I entered into conversation with her, and found her charming. French was evidently her native tongue, and she spoke no other; there was just enough of shyness in her manner to increase its fascination, without giving it a tinge of awkwardness, and with her vivid blush, her evident gratitude for any attention paid her and her litle playful confidences about the Parisian convent she had just left, I thought her one of the most lovable creatures I had ever seen. It will be asked by the uninitiated, and, among the rest, by you- why this fair being was set apart in the way I have described, and why she was like a tabooed creature, or rather a Pariah from which men and women seemed to shrink as from an unholy thing. Dear ---, it was this. Within the veins of this fair and delicate girl ran a few drops of that dark blood, which is supposed by many-- I fear, indeed, by most in America-- to place the individual cursed by so hideous an accident without the pale of social existence. It mattered not that this poor girl was fair in form and gentle and kind in nature-- her mother was a Quadroon!
...... And how little, how very little, was she herself aware of the many and deep mortifications that awaited her! [She had been at school in Paris for eleven years]

She mused alone! Nor did she question why
No friends came near her to console or cheer;
Alone she check'd the ever-rising sigh,
Alone she shed the agonizing tear.

Once she was blest: the spring-time of her life
Was then as cloudless as a summer's day;
Unfit to battle in the tempest's strife,
Love flung its radience o'er her gladsome way.

Poor nameless girl! Those joyous hours have fled;
Gay flowers no more thy weary path adorn;
Thou stand'st amongst thy garlands crush'd and dead,
The heart well nigh as withered and forlorn.

Thy gentle head in meek affliction bend;
Glean, if thou canst, from solitude relief;
At least 'tis something, though without a friend,
That none can mock the lonely slave-girl's grief.

Poor victim of an erring nation's curse,
Is there no pitying heart to mourn thy woes,
To feel that life can show few sorrows worse
Than those that wait thee ere thine own shall close.

Bereft of all that makes existence dear,
Thy smiles the wealthy and the gay may buy;
The hidden griefs thy sole possession here,
The only hope that's left thee is to die!

"Hesperos: or, Travels in the West," by Mrs. Houstoun. Volume I.
http://rs6.loc.gov/ammem/htnhtm/htnhome.html (Takes you to American Notes: Travels in America 1750-1920)
http://rs6.loc.gov/ammem/htnhtml/hbtnbibAuthors02.html (to authors index, including Houstoun).