Category talk:Crystals

What is the difference between a crystal and a crystalline solid?
Category:Crystals and Category:Crystalline solids are two different categories, of which Category:Crystals is a subcategory of Category:Crystalline solids. However, the article Crystal seems to imply that a crystal and a crystalline solid is the same thing. So, why are do we have two categories? Is there any crystalline solid that is not a crystal? Unless there is a clear difference, I propose that we merge Category:Crystalline solids into this category. —Kri (talk) 12:06, 24 June 2017 (UTC)