Fig. 1 Virgin of the Rocks, National Gallery, London

Leonardo da Vinci was a consummate observer of nature.  His scientific curiosity led him to capture natural objects not only beautifully, but accurately as well.  His sketches and drawings serve as a record of the geological formations he saw in his travels.  Most of his life was spent in Italy, traveling between Florence and Rome, but it was in 1482, when he went to Milan to work for Ludovico Sforza, that he became fascinated with Alpine geology.  He spent considerable time in the mountains observing the structure of rock formations, the presence of fossils imbedded in stone and the natural characteristics of water and air.  He memorialized his observations in his note book, now known as the Codex Leicester, which details his thoughts and observations on geology, hydrology and the effects of water and air on the earth.  He revealed his observations in his paintings and drawings by precisely depicting geologic formations which, at the time had not been named, but which are readily identifiable to a modern geologist.

Viewed from a geological perspective, all of Leonardo’s paintings and drawings reveal a remarkable fidelity to nature.  The Virgin of the Rocks (Fig. 1) in the National Gallery in London, attributed to him, displays no such fidelity.  If we compare it to the Virgin of the Rocks in the Louvre (Fig. 2), whose geological accuracy is astounding, we cannot help questioning whether Leonardo himself painted the background in the National Gallery painting.

The history of the two paintings is also ambiguous and thus not very helpful to scholars who have researched the question.  Several ideas have been set forth, however, with inconclusive results (see Appendix for historical details).

The fact that attribution of the two works has been unresolved and the subject of such scrutiny throughout history suggests that new diagnostic means of determining authenticity are in order.  A comparison of the representations of geological formations in the two paintings offers such means.  It seems unlikely that the same person could have portrayed geological formations so accurately in the Louvre work and so incongruously in the National Gallery painting.

The Virgin of the Rocks in the Louvre is a geologic tour de force because of the subtlety with which Leonardo represents a complicated geological formation (Fig. 3). The grotto is made of weathered sandstone dissected by a layer of harder rock.  At the top of the grotto are rounded (spherically weathered) mounds of sandstone, a sedimentary rock.  Above the Virgin’s head is a rock that juts out in vertical relief.  This is diabase, an igneous rock that was injected as a molten liquid and spread over the sandstone, forming a band (or a sill) several feet high.  The rock contracted as it cooled, forming vertical (columnar) joints.  Directly above the Virgin’s head is a horizontal crack in the rocks called a basal or bottom contact.  This is the seam between the diabase about and the sandstone below.  The column of diabase extends upward until it meets another horizontal contact surface and the rock formation changes to sandstone at the top of the grotto.

The rocks that extend from below the basal contact line near the Virgin’s head down to the foreground are sandstone, like those at the top of the grotto.  The texture and rounded weathering pattern of the sandstone are the same below the basal contact as they are at the top of the grotto. In the foreground, the sandstone has not been heavily weathered and has therefore retained its highly defined horizontally layered (or bedded) structure.  The diabase sill at the center of the formation is harder and less prone to erosion, hence its sharp edges and vertical relief.

The jagged rocks rising from a blue-gray mist in the background are remnants of erosional processes that stripped away the overlying softer rock and left the harder rock remaining.  These formations have been subtly yet accurately depicted, consistent with Leonardo’s unwavering commitment to geological realism.

What is especially intriguing is Leonardo’s placement of vegetation in the picture, not simply to achieve aesthetic effect, but rather according to the location where such plants would grow. At the top of the grotto, the sandstone would have decomposed sufficiently to allow roots to take

hold.  This is true for the plants growing in the foreground and in the background.  No plants are growing out of the diabase, however, since it is too hard and resistant to erosion to provide a suitable habitat for plant growth.

An observer with some knowledge of geology would find that the rock formations represented in the National Gallery work do not correspond to nature, as do most of Leonardo’s drawings and paintings.  It seems unlikely that Leonardo would have violated his knowledge of geology, in favor of abstract representation, considering that he executed an even more geologically complex picture in the Virgin and St. Anne (1510), finished after the National Gallery painting.

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All we know about Leonardo suggests that he had too much respect for the nuances of natural beauty to ignore them.  The rocks in the National Gallery painting are synthetic, stilted, grotesque characterizations.  They miss the point geologically.  Looking at the painting, above the Virgin’s head, there is no change in the texture of the rocks to indicate the presence of the diabase sill.

The vertical joint patterns continue upward without interruption.  The type of rock remains constant, in comparison to the changes in rock form in the Louvre work.  In the background, a glacial lake or possibly a fjord is highly suspect.  Fjords do not exist in Italy and it is highly unlikely the glacial lakes of the Lombard region would have such steep relief surrounding them. In the foreground, the rocks are not finely bedded.  They are roughly weathered and massive, giving the appearance of limestone rather than sandstone.  The presence of limestone would be incongruous in this geological setting.  The lack of knowledge on the part of the painter of the National Gallery work seems to exclude the possibility that it was Leonardo.

The Louvre painting on the other hand, shows a congruence in the rocks.  Both the sandstone and diabase are weathered and the fracture surfaces are weathered in accordance with the respective hardness of each of the rocks.  The result is an accurate portrayal of the sandstones, which have been rounded by water and wind erosion in contrast to the diabase, which is much more resistant, and therefore retains its structural characteristics.  Leonardo is able to capture this contrast first, by having an understanding of how the rocks actually look and then representing this appearance realistically through his use of light and color.  Leonardo’s use of sfumato and shading suggest the appearance of a moist, musty grotto.

The difference in the two sets of rocks may not be immediately obvious to the layman.  Yet given Leonardo’s passion for geology and his genius for painting, closer evaluation suggest that the Louvre rocks are Leonardo’s and the National Gallery’s are not.

Leonardo’s observational geology is far more accurate than the geology of Renaissance theorists.  Such extraordinary knowledge provides us with an unbiased method of distinguishing his work from that of his many imitators and followers. READ MORE Precise geology is an index to authenticity.  It can serve as Leonardo’s inimitable trademark.  As we continue to examine his work from this perspective, as I hope to do in future studies, we can be relatively sure that no other artist of his time understood geology so well.

Other artists

Historical Details

In April, 1483, the Brethern of the Immaculate Conception commissioned Leonardo and the DePredis brothers to paint an altarpiece for their Chapel,(Fig.4) San Francesco il Grande, located in Milan.  The painting, which would be installed in an elaborately made frame; also part of the commission, was to be the Virgin of the Rocks (Louvre), which Leonardo completed between 1483-86.

In about 1490, the DePredis brothers, still working on the project, appealed for additional payment; pointing out that the Virgin’s painting had been completed but the frame alone cost the entire 800 lire fee to which the artists had originally agreed.  They requested that the “oil painting of Our Lady” (Virgin of the Rocks) be withdrawn from the commission as others had offered to purchase it.  The petition was denied.  In 1503, Ambrogio De Predis tried again and the case was dismissed.

It is not clear whether the Louvre work was hanging in the Chapel or was in Leonardo’s possession during the years of legal wrangling.  Documents pertaining to the final settlement in 1506, however, specified that Leonardo was to finish, or have someone else finish the painting with two years.  For this he would receive 200 lire.  Thus one version of the disjointed history of the two works would have it that Leonardo finished the Louvre painting in 1486 and received no compensation for it as late as 1506 while the second painting was started in about 1503 and was finished by 1506.  The latter painting now hangs in the National Gallery.

Other accounts theorize that the Louvre work was hanging in the Church of San Francesco il Grande in 1503, but that groundwork of a copy was in the DePredis workshop.  In 1506, the year the matter was settled.  Since Leonardo had not been paid for the first painting, it was forfeited to him, and he in turn, gave it to the King of France.  At the same time, for one half the original payment he had been asking for the original version, Leonardo gave the Confraternity the groundwork, which he agreed to finish in two years.  Angela Ottino della Chiesa1

argues that this is the London version.

The Louvre version was first mentioned as part of the royal collection at Fontainebleau in 1625.  The London version, which remained in the church of San Francesco il Grande in Milan until 1781, was taken to the hospital of Santa Caterina in Milan and purchased in 1785 by the English painter Gavin Hamilton.  It was in the collection of the Marquis of Landsdown, then the Earl of Suffolk, before entering the National Gallery in 1880.

Fig. 2 Virgin of the Rocks, Louvre, Paris