I found crystal plants in the wasteland and harvested them. Plant them like a normal plant and just like the "water" option it will give you the option to imbue a neutral (starting/default) crystal with any emotion you desire. I think the plant has to grow up into getting leaves in order to get that option. Imbuing it many times with emotion raises the % of that emotion giving you the crystal type you want.
Side note on imbuing an emotion: it's helpful to do several at the same time as there is a small wait period to imbue again. It's not too long (maybe an IG hour). You can imbue a mature plant or a bearing plant, but you don't have to imbue it all the way for the flowers to change to the emotion.
Celebrating over 10 years of the Sims
All of Sims 1 save Hot Date
All XPs of Sims 2
All XPs of Sims 3 + OLS