Here is an awesome essay/paper on natural pigments:

http://naturalpigments.com/education/article.asp?ArticleID=116

http://naturalpigments.com/education/article.asp?ArticleID=116

http://naturalpigments.com/education/article.asp?ArticleID=116

http://naturalpigments.com/education/article.asp?ArticleID=116

http://naturalpigments.com/education/article.asp?ArticleID=116

http://naturalpigments.com/education/article.asp?ArticleID=116

Trying to figure out how to smash these sea stones into pigment…..