| The mineral is found as small pink to gray masses of microcrystals in quartz-feldspar pegmatites and veins in association with astrophyllite, riebeckite, and zircon. |
| On the other hand, there is evidence that long-term exposure to asbestiform riebeckite can be dangerous. |
| Within this granite are darker bands richer in iron because they contain the pyroxene mineral aegirine and the amphibole mineral riebeckite. |
| Willman reported astrophyllite, biotite, molybdenite, and riebeckite associated with smoky quartz and microcline on Mount Kineo at North Cheyenne Canyon. |
| Several pools of syenitic magma were separated from the main body of the melt, each eventually being emplaced as quartz syenite, fayalite granite, and riebeckite granite. |
