User blog comment:Goldensunsheba/I AM OFFICIALLY DEAD/@comment-27304481-20160810043227

Answer: Diamonds are surprisingly easy to shatter. Cutting it can only be done in those ways, but natural fault lines are present that are surprisingly easy to cause to break, due to a diamonds brittle nature.

Nonetheless, it's pretty obvious Rose Quartz didn't do that. She's Rose Quartz. She specifically denied the pitch that equaled shattering a diamond. Unless the guilt from shatterring her diamond caused her to snap and refuse any shattering ever(inspiring her to invent bubbling magic), this would go against her character.

So Rubellite is safe as far as her reputation for shatterring a diamond. (Lol, now I am just envisioning a three way war with rose attacking HW for being caste, rose attacks rube for shatterring, rube attacks RQ for trying to take gems away from her empire, rube against HW to take over, and HW just scrambling to keep everything how it was short two diamonds)