Estraeah would never claim to be an expert on crystals. However, with her limited knowledge due to researching potential magical properties, she presumes they are likely quartz. The geometry appears correct, and quartz comes in most colors.
Even so, the range present here is extraordinary. Every hue, varied from light to dark. It is almost as if every color exists in this cavern. To Estraeah, this feels undeniably imaginable.