Polychrome hard stone marquetry was the subject of increasingly large orders at the end of the 16th century and in the 17th century. This flagship technique of the Florentine and Roman workshops of the Renaissance consists in using colored stones, cut and adjusted, finely polished to create images. Like the art of painting on stone, this technique is part of a movement of renewed interest in the 1580s for the collection of hard stones. Indeed, drawing on the classical tradition and driven by the development of a sensitivity to the products of the natural world, the pictorial potential of stones at that time aroused the enthusiasm of collectors and artists. Thus, our altarpiece is presented as a lightened and portable version of the sumptuous marble and hard stone altars which then adorned the churches of Baroque Rome. In the form of an architectural aedicula supported by Corinthian columns with gilded bronze capitals, its pediment and console are enhanced with plates imitating lapis lazuli, as well as sumptuous polished hard stones. At the heart of the altarpiece, an arched niche houses a superb gilded bronze made after the Charity of Algardi (c.1635-1650), a key player in Baroque sculpture in Rome. Represented in the form of a young woman giving the breast solicited by several children, Charity here wears a richly ciseled coat. It is surrounded by four cherubs in gilded bronze which must have held in their hands parchments whose inscriptions accompanied and guided the meditation of the patron of this private altar to Charity.