Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by function]
6. coating (material)
7. [coating by composition or origin]

Additional parents:

1. top of the aat hierarchies
2. Physical Attributes Facet
3. Conditions and Effects
4. conditions and effects by specific type
5. conditions and effects for landscape

Anotations

Scope note:

Thin mineral coating composed of iron and manganese oxides deposited on rock surfaces in desert areas. The reddish brown or black desert varnish layers form as moisture evaporates leaving behind dissolved mineral residue which wind abrasion polishes over the course of centuries. Some petroglyphs are images incised in desert varnish, a technique which exposes the lighter stone beneath.