This achievement requires you to beat Marathon Mode by making a cluster, line, or flower of Black Pearls.
The easiest way to do this is to make a cluster, as it only takes 3 Black Pearls, whereas a line is 5 Black Pearls and a flower is 6 Black Pearls. Since Black Pearls are more difficult to make, that is why I say go for the cluster. This achievement will require lots of skill and patience. Some methods or tips are:
1. Make a link of 8 stars in a line, preferably vertical, of 4 stars, leave a colored hex in between, and then have 3 more stars on top. Then, rotate a star into the middle. What this will do is create 4 rubies, because the game will see 4 simultaneous lines of 5: 1-5, 2-6, 3-7, 4-8. Then make a link of 7 stars somewhere else to avoid clusters to get 3 more rubies. Line them up so that there are either 3 on each side or 4 and 2, with a colored hex in the middle. Then, rotate your 7th ruby into that spot. The game will see 3 lines, and give you 3 black pearls. Use emeralds, and other starflowers, or just keep rotating until you make these 3 into a cluster.
2. Create as many Starflowers as you can in the beginning levels to avoid having new colored tiles and bombs get in the way of creating them. From there, begin chaining together your Starflowers to make Rubies. Once you have made enough Rubies to create 3 black Pearls, do so. I suggest making one at a time, that way you don't accidentally make clusters. Also, do not use all your Starflowers at once. Always make sure that you have at least 2 Starflowers to be able to continue making more, as you progress it will get more and more difficult to make Starflowers.
Video Guide:
Credit to Games Master