In the Hindu religious tradition, the tulsi, or holy basil, plant serves both as an important symbol and also as a popular medicinal remedy.
Diamond use to be the hardest known natural substance now it is the mineral lonsdaleite at 58% stronger then diamond is the first the second hardest is wurtzite boron nitridâ¦e at 18% stronger then diamonds they are both extreamly rare natural minerals sources http://www.newscientist.com/article/dn16610-diamond-no-longer-natures- ...
To summarize Ankit and Mads's answers: it depends on what strength you are looking for. Some people are interested in hardness. Diamond is the hardest substance discovered to date, but note that hardness here refers to scratch resistance. Diamond can be shattered quite easily; if you could obtain a sheet of diamond and hit it, it would break like glass. In other words, you probably wouldn't want to make a diamond car or building.