Final answer:
While many stones are oxides and hydroxides, the Earth's crust primarily consists of silicates. Stones such as kidney stones are indeed composed of compounds like calcium oxalate and calcium phosphate. However, silicates and compounds other than oxides and hydroxides, including those from extraterrestrial sources, are also common.
Step-by-step explanation:
You are partly correct that many stones are oxides and hydroxides, but there is more diversity in mineral composition than just these two groups. For instance, hydroxyapatite, a mineral you mentioned, is indeed a complex phosphate mineral with the formula Ca5(PO4)3(OH) and may contain trace elements like iron which can alter its color. The formation of kidney stones, usually comprised of calcium oxalate (Ca(O₂CCO₂) H₂O) or calcium phosphate (Ca3(PO4)2), is a direct example of stones formed from oxides and hydroxides.
However, the majority of the Earth's crust is made up of silicates, which contain oxygen and silicon. Silicates, with the basic unit of SiO4, are incredibly varied and form many different structures and minerals, representing about 90% of the Earth's crust. Additionally, some stones of extraterrestrial origin, often referred to as 'meteorites', are primarily composed of silicates or metal alloys, rather than oxides or hydroxides.
It's essential to consider that many metal oxides are insoluble and are termed base anhydrides because they can react with acids even if they don't form hydroxides in water. The nervous system with transition metals can form hydroxides that are often hydrated oxides compounded with metal ions, oxide ions, and water of hydration.