Why are minerals important to your story?

Granted, knowing the scientific reason your planet was created may not be all that important to your story, unless it was created for a purpose, but it can lead to what chemicals and minerals your planet is made of. Knowing what chemicals and minerals are on your planet is important because that is what creates life. A planet with no natural form of carbon is unable to create carbon based life forms, although life could still be created through another chemical or your species may have come from another planet somewhere in its history. Whether the people know that centuries later is up to you. Also knowing what minerals your planet has or doesn’t have can be helpful in figuring out what technology is made of and how it differs from human stuff in colors or strength or weight. Although you could merely assume your planet has the same minerals as Earth, here is where you can develop new chemicals or minerals to speed up the technological timeline so they got to space before humans or create things currently impossible on our planet.
Something else to consider when thinking about minerals is what your species needs to survive. Humans need seventy minerals in their diets to stay healthy throughout life. Those minerals humans get by eating plants that have soaked up those minerals from the soil they were raised in and each one is needed to balance all the minerals and chemicals in your body. Years of imbalance lead to degenerative diseases in old age or minor annoyances throughout one’s life. If you plan to have humans on your planet for whatever reason, it would be good to look at how the minerals and chemicals on your planet, or lack thereof, would affect the health of those humans. How do they adapt?
One last thing to think about today is how your planet’s gravity differs from Earth’s gravity. Although scientists argue about how gravity affects evolution, it is agreed that the planet could not exist without the gravity it has. A planet with less gravity would be held together a little looser and things may float around a more than on Earth, or more accurately, fall slower. A planet with stronger gravity may be smaller, more compact than Earth and everything on it not grow as tall. Also, humans would react differently to a different gravity and other species would react differently to our gravity if there’s differed.
Once all these things have been decided, we can think on topography and why to make a map of your planet, as we will in the next installment.