// Old Red Sandstone (TdG99)
#declare TdG_OldRedSandstone = 
   material {   
      texture {      
         pigment {
            bozo
            pigment_map {
               [0.0 color rgb <0.6, 0.1, 0.1>]
               [0.2 color rgb <0.4, 0.05, 0.0>]
               [0.8 color rgb <0.75, 0.25, 0.1>]
               [1.0 color rgb <0.6, 0.1, 0.1>]
            }
            scale  <40.0, 0.3, 25.0>
            rotate    <-10.0, 0.0, -15.0>
         }      
         scale  0.5
      }
   }

// An eroded sandstone (TdG 99):
#declare TdG_Sandstone = 
   texture { // T_Grnt12
    pigment {
     granite
     pigment_map {
       [0.000 color rgb <0.996, 0.969, 0.8>]
       [0.154 color rgb <0.996, 0.682, 0.604>]
       [0.308 color rgb <0.906, 0.82, 0.714>]
       [0.444 color rgb <0.816, 0.631, 0.537>]
       [0.615 color rgb <0.89, 0.792, 0.675>]
       [0.812 color rgb <0.973, 0.627, 0.627>]
       [1.000 color rgb <0.996, 0.969, 0.8>]
     }
     turbulence 0.6
     ramp_wave
     scale  <200.0, 3.0, 150.0>
     rotate -5.0 * z
    }   
    normal {
     bozo , 5.0
     bump_size 0.8
     turbulence 0.7
     ramp_wave
     rotate -90.0 * x
    }
   }
   texture { // T_Grnt17a
    pigment {
     granite
     pigment_map {
       [0.000 color rgb <0.027, 0.012, 0.012>]
       [0.034 color rgbf <0.851, 0.812, 0.741, 0.235>]
       [0.342 color rgbf <0.71164, 0.694, 0.82, 0.839>]
       [0.462 color rgbf <0.631, 0.506, 0.471, 0.608>]
       [0.632 color rgbf <0.851, 0.812, 0.741, 0.922>]
       [0.983 color rgb <0.027, 0.012, 0.012>]
       [1.000 color rgb <0.996, 0.969, 0.8>]
     }
     turbulence 0.6
     ramp_wave
     scale  <150.0, 3.0, 200.0>
     rotate    <5.0, -10.0, 0.0>
    }   
    normal {
     bozo , 5.0
     bump_size 0.8
     turbulence 0.8
     ramp_wave
     rotate -90.0 * x
    }
   }
   texture { // T_Crack1
    pigment {
     granite
     pigment_map {
       [0.000 color rgbf <0.0, 0.0, 0.0, 0.6>]
       [0.040 color rgbf <0.0, 0.0, 0.0, 1.0>]
       [0.041 color rgbf <0.55, 0.09, 0.09, 0.8>]
       [0.970 color rgbf <0.33, 0.33, 0.33, 0.9>]
       [0.971 color rgbf <0.0, 0.0, 0.0, 0.9>]
       [1.000 color rgbf <0.0, 0.0, 0.0, 1.0>]
     }
     turbulence 0.85
     ramp_wave
     scale  <1.0, 2.0, 1.4>
     rotate    <-10.0, 0.0, 20.0>
    }
   }