Internal graining is caused by irregularities in a diamond’s crystal growth. It’s appearance can take the form of lines, angles, or curves, and it might be whitish, colored, or reflective. Internal graining can give part or all of the stone a hazy texture, but is usually small, and it is fully considered in the assessment of a Clarity Grade. It might be composed of fine, colorless lines. Some types of internal graining resemble falling rain or sleet, while others might look like vinegar in oil. These growth lines are usually hard to detect in diamonds.