Crystals:
* Quartz: Often forms clear, smooth, six-sided crystals with pointed terminations.
* Calcite: Can form a variety of shapes, including smooth, rhombohedral crystals.
* Fluorite: Often forms cubic or octahedral crystals, which can be very smooth.
* Gypsum: Can form clear, smooth, tabular crystals.
Other Minerals:
* Opal: Known for its smooth, rounded, and often iridescent surfaces.
* Obsidian: A volcanic glass that can be smooth and glassy.
* Jasper: A variety of chalcedony that can be smooth, polished, and highly patterned.
* Agate: Another chalcedony variety that often forms smooth, banded patterns.
Please note: These are just a few examples, and the specific shape and smoothness of a mineral will depend on its specific variety, formation, and how it has been handled.
Could you provide more details about what you're looking for? For example, are you interested in a specific color, size, or geological location?
