is this just iron-stained quartz? very weird looking pattern

this is one of my FAVORITE crystals, but i realized after two years, i don’t even know what it is! it’s got an odd composition, and i’ve got questions.

this crystal tower looks to have the color of an iron-stained quartz, but has additional deposits. they feel raw (not smoothed) even though the rest of the crystal has been smoothed.

especially confused about the very dark deposits. are they just iron?

what do you think? leave an educated guess. show me if you have a crystal like this, or can find a picture of one online!