[flamberge]

It was apparently castor beans, but why would it take more than a few minutes to recognize castor beans?

Because they were dried and crushed into a white powder.

Castor beans contain small amounts of ricin, which can be extracted from them. The extract is a white powder.

[ltc8k6]

No, the white powder was harmless and sent to Ted Cruz. The letters to Mattis, Richardson, and Trump contained unprocessed castor beans.