Some Martindale readings for different kind of general outdoor fabrics as collected from a 1986 Finnish study:
Cotton twill, 8-9 oz/ft2 = 25,000 - 47,000
50/50 % Polyester-cotton twill, 8-9 oz/ft2 = 25,000 - 90,000
Wool gabardine, 9 oz/ft2 = 50,000 - 83,000
60/40 % Polyamide-cotton twill, 7...