Leonardo's Geology: The Authenticity of the Virgin of the Rocks

by Ann C. Pizzorusso

30 Fifth Ave. New York, New York 10011, U.S.A.


There are two versions of Leonardo da Vinci's Virgin of the Rocks, the first in the Louvre, and the second in the National Gallery. There has been some debate as to whether Leonardo painted any or all of the National Gallery version. So far, research on the two works has centered upon an analysis of historical documents. The author, a geologist, has studied Leonardo's paintings and drawings from a geological perspective. Based on the geological differences noted between the two paintings of the Virgin of the Rocks, the author concludes that Leonardo did not paint the rocks in the National Gallery work.

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 notebook, now known as the Codex Hammer, 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.

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

Various arguments have been made over the centuries calling into question the attribution of the National Gallery painting to Leonardo. Scholars have analyzed the brush strokes, undertaken document searches and tried to prove definitively that Leonardo painted the National Gallery work. However, there has always been some doubt and many unanswered questions concerning its authenticity.

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.

The fact that the two works have been the subject of such historical scrutiny suggests that other diagnostic means of determining authenticity, apart from a review of the documents are in order. One means is provided by comparing the respective geological representations of the two paintings. It seems unlikely that the same person could have portrayed geological formations so accurately, in the Louvre work, and then so incongruously, as in the National Gallery painting.

The Virgin of the Rocks in the Louvre is a geological tour-de-force because of the subtlety with which Leonardo represents a complicated geological formation (Fig. 3.). The grotto is made of weathered sandstone which has been dissected by a layer of harder rock. At the top of the grotto are rounded weathered mounds (spherical weathering) of sandstone, a sedimentary rock. Above the Virgin's head is a rock with vertical relief. This is diabase, an igneous rock. The diabase was injected as a molten liquid, forming a band (sill) several feet high over the Virgin's head. Since it was a molten liquid when it spread over the sandstone, it contracted as it cooled, forming vertical or columnar joints. Directly above the Virgin's head is a horizontal crack in the rocks, called a basal or bottom contact, which is the seam between the diabase above 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 below the horizontal line (basal contact), near the Virgin's head, and extending down to the foreground are sandstone. This is the same stone that appears at the top of the grotto. The texture and rounded weathering pattern are the same below the basal contact as in the rocks at the top of the grotto. In the foreground, the layered (bedded) sandstone has not been heavily weathered, thereby retaining its highly defined horizontal layered structure. The rocks in the center, forming the diabase sill, are harder and more weather resistant. They are therefore, less prone to erosion, have sharper edges and more vertical relief than the sandstone.

The jagged rocks in the background, rising from a blue-gray mist, are remnants of erosional processes which 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 for 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.

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. 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.


In April, 1483, the Brethren of the Immaculate Conception commissioned Leonardo and the De Predis brothers to paint an altarpiece for their Chapel, 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 1483-1486.

In about 1490, the De Predis 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 within 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 De Predis 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 Chiesa 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 Lansdown, then the Earl of Suffolk, before entering the National Gallery in 1880.


basal contact---lower plane where two different types of rock come in contact with each other.

bedding---planes dividing sedimentary rocks of the same or different rock types.

contact---uUpper plane where two different types of rock come in contact with each other.

diabase---a rock of igneous (volcanic) origin. Dark in color, very hard, low permeability.

erosional remnants---rocks which, being harder than the rocks lying above or beside them, are left behind after other, less resistant rocks are eroded away by water or wind.

dip---angle at which rocks are found in-situ.

glacial lake---a long, deep lake having high steep walls and side streams entering from high-level valleys by cascades or steep rapids.

igneous rock---a rock which originated as a result of volcanism and solidified from molten material.

joint---fracture in rock, generally more or less vertical to bedding, caused as a result of cooling of the molten rock. Fractures normally occur in parallel patterns.

limestone---a sedimentary rock consisting chiefly of the mineral calcite (calcium carbonate)

sill---an intrusive body of igneous rock of approximately uniform thickness and relatively thin compared with its lateral extent, which has been placed parallel to the bedding of the overlying and underlying rock.

spheroidal weathering---a form of chemical weathering in which concentric shells of decayed rock are successively loosened and separated from a block of rock by water penetrating the bounding joints or other fractures and attacking the block from all sides. It is similar to the larger-scale exfoliation produced usually by mechanical weathering.

unstratified---not formed or deposited in strata; with an absence of layering.

(Adapted from Dictionary of Geological Terms, 3rd Ed., Robert L. Bates and Julia A. Jackson, eds. Anchor Press, New York.)

Copyright ISAST 1995.

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