* Streak: Sandstone is a clastic sedimentary rock, meaning it's formed from fragments of other rocks. The color of the streak, which is the color of the powder left behind when rubbed on a streak plate, is determined by the dominant mineral in the sandstone.
* Quartz Sandstone: Will have a white or colorless streak because quartz is colorless and has a hardness of 7.
* Feldspar Sandstone: Will have a white or slightly pink streak because feldspar is usually white or pink and has a hardness of 6.
* Arkose Sandstone: Will have a reddish or pink streak if it contains a significant amount of feldspar.
* Greywacke Sandstone: Will have a dark gray streak because it contains a mixture of quartz, feldspar, and rock fragments.
* Hardness: The hardness of sandstone varies greatly depending on the minerals present and their cementing material.
* Quartz Sandstone: Is harder because quartz is a hard mineral.
* Feldspar Sandstone: Is softer because feldspar is less hard than quartz.
* Arkose Sandstone: Is also softer than quartz sandstone.
* Greywacke Sandstone: Is generally softer because it contains a greater variety of softer minerals.
However, it's important to note that:
* Sandstone is often porous and friable, meaning it's relatively soft and easily broken.
* The hardness can also be influenced by the cementing material that binds the sand grains together. This can be calcite, silica, iron oxides, or other minerals.
In summary: You can't determine the streak and hardness of sandstone just by knowing it's "sandstone." You need to consider the specific minerals present and the type of cementing material.
