Surface material is of utmost importance in Jorge Rodriguez-Gerada's practice. The artist, who is known for creating massive land art portraits visible from aerial views, recently presented a new series of work titled "Fragments of Humanity" for his current solo show in White Walls Gallery's project space. For "Fragments," Rodriguez-Gerada utilized pieces of stone from his adopted home of Spain. Culling materials for buildings that are slated to be demolished, the artist chose surfaces with over 500 years of history, reworking them to create a line of continuity from their past to the present. His series of mixed-media portraits on wall surface fragments look so fragile they could break if they weren't wedged between the panes of glass in their frames. This delicate series is anchored by a weighty sculpture carved from a limestone pillar. "Fragments of Humanity" is on view through June 7 at White Walls in San Francisco.