Generally, the commercially available Hay Absolutes are viscous liquids, dark amber, dark green or brownish green in color, occasionally they are soft masses of olive-brown color. The odor is powerful and extremely sweet, quite diffusive, coumarin-like and faintly herbaceous, very uniform and tenacious. The undertone is almost jam-like sweet, reminiscent of figs or preserved prunes in odor type. There is a distinct difference among the hay absolutes extracted from hay without flowers, with flowers, or with seed.
Arctander, Steffen . Perfume and Flavor Materials of Natural Origin (p. 338).