some examples of minerals in iron-rich rocks containing oxides are limonite hematite and magnetite. an example of a mineral in iron-rich rock containing carbonates is siderite and an example of minerals in an iron-rich rock containing silicate is chamosite. they are often interbedded with limestones shales and fine-grained sandstones.
the easiest way to find most minerals is to find a cave that is already there and explore it as opposed to digging randomly. there are some minerals that are almost always near the bottom such as redstone and diamond. but even with diamond you're more likely to find it in a cave (usually filled with lava in that case)
just so you know i knew about the treasure chest in yokmir cave i chose to leave it out because chests are single harvests. this does not apply to the random boxes at floating empire or the ore rocks which can be continuously reaped each day. but you can sell it then buy from raven- hence infinite silver.
hematite is one of the most common minerals. the color of most red and brown rock such as sandstone is caused by small amounts of hematite. it is also be responsible for the red color of many minerals. non-crystalline forms of hematite may be transformations of the mineral limonite that lost water possibly due to heat.
hematite is dense and hard it is the most important ore of iron because of its high iron content and its abundance.the mineral occurs in various habits: steel-gray crystals and coarse-grained varieties with a brilliant metallic luster are known as specular hematite; thin scaly forms make up micaceous hematite; and crystals in petal-like arrangements are called iron roses.