The first one, "was revealed" makes it passive,
Answer: It's the amethyst.
Explanation:
Explicit information refers to clear and concise information. It is not implied such that the recipient would have to figure it out.
In the text above, all the sentences were implicit information except the last one as they alluded to a gemstone without naming the gemstone thereby making their information implied.
The last statement explicitly states that the gem is Amethyst instead of implying it.
