Answer:
I can be winding and I can be straight. I can be smooth and I can be rough. Sometimes both. I start out black but fade to brown. My favorite colors are yellow and white and I love stripes and dashed lines.
Brown I am and much admired; many horses have I tried; tire a horse and worry a man; tell me this riddle if you can.
I have fangs and enjoy piecing holes with a single bite.
Born of sorrow, grow with age, you need a lot of me to be a sage. What am I?
Though not a plant I have leaves. though not a beast I have spine. Though many wouldn't need me I am more valuable than wine.
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.