This page lists the possible prizes from opening Chaos Balls and their relative percentages of getting them. This is just a summary of results combined from two major tests. About 45,000 Chaos Balls were opened! The results here are therefore approximate and rounded to the nearest tenth of a percent. More details may be found here.

Item	Percent Chance
1 Chaos Smelting Stone	0.85
1 Platinum Blessed Iris	2.2
1 Blessed Iris	2.2
1 Heaven Stone	5.0
10 Candy	6.0
1 Experience Scroll or 1 Effort Scroll or 1 Lucky Scroll	5.5
1 Item Drop Booster or 1 Experience Point Booster or 1 Skill Point Booster	9.5
5 Physical Attack Mineral (level 12) or 5 Magical Attack Mineral (level 12) or 5 Physical Defense Mineral (level 12) or 5 Magical Defense Mineral (level 12)	9.8
10 Great HP Potion	8.7
10 Great MP Potion	11.0
3 Tool Aid	18.0
10,000 Gold Coins	11.4

Note: Yes, the total percent is 102.8, this is due to the margin of error in the combining of the two data sets and the inherent margin of error in those values.


Thanks to jaretlafoudre and roguej91