What kind of rock do I have, how can I tell what kind of rock this is?
Use this chart for images to help you identify what type of rock you have. If you don't see and exact image try to match it with the most similar and then look at the category or family that the rock is in.
Table of Grit Choices for Rock Type
We have created a lookup table that allows you to match the type of rock that you are tumbling with the specialty grit kit that you can use.
The most interesting rocks to tumble are igneous. This is because Igneous rocks are categorized by their texture and composition. Igneous rocks are produced directly from hot molten rock, or magma, coming from deep within the Earth. Luckily we were not around at the time but we have figured that as magma cools the elements come together to form and crystallize. We all know that this crystallization was the basis.
The exciting part and the cause for variety and the wonder of the visual differences in minerals (rocks) crystallizing at different temperatures. This caused differences in grain size and texture and hardness. When magma cools slowly, some individual mineral grains grow larger or smaller as a group. Where the magma cools quickly, like lava or basalt, the separate mineral grains are very small. We classify Igneous rocks on the very basis of that size and naturally formed arrangement of each crystal or present mineral.
Just Remember the Big Difference
There are type groups of Igneous rocks: those composed of felsic and mafic rocks. Felsic igneous rocks are composed mostly of feldspar and quartz (silica). Mafic Igneous rocks are composed mostyl of minerals with lots of iron and magnesium.
This will make it easy to understand when making visual identification.Felsic rocks are usually light to intermediate in color. Mafic igneous rocks are usually dark. Just Remember Felsic - light. Mafic - dark. To make it super easy think just about quartz, you know how you can see through it, well it's felsic. You remember, light. That's it, and mafic the other side is dark
We all know about sedimentary rocks, the really layered rocks that sometimes peel away like onions.. Sometimes made of small pieces of shells, plant and animal remains, and weathered fragments of other rocks. These sediments have been moved by the geologic workings of the spinning earth. Think rivers, waves, winds, or glacial ice.
And there are some pretty worthwhile rocks to tumble in this group but it is more limited than Igneous rock choices. Sedimentary rocks are a lot more mono-dimensional in their appeal and they have a lot less intermingled beauty. You just can beat a crazy lace Jasper for a varietal concert of form and color.
Sedimentary deposits are compacted and cemented by the mineral matter coming out of water as it moved through the holes between the sediment particles. Pores are holes or voids in the sedimentary rocks had not been filled with other material. We call these sedimentary rocks clastic (meaning broken pieces) rocks. Not only are there water elements involved here. There are other sedimentary rocks which may be formed by chemical precipitation from water as a delivery mechanism and these chemicals consolidations are made up of organic fossil remains.