A topaz
The mineral that can be scratched by a penny is talc. Talc is the softest mineral on the Mohs scale, with a hardness of 1. A penny has a hardness of around 3.5 on the Mohs scale.
apatite with a steel knife feldspar with window glass
Copper sulfide minerals, such as chalcocite and bornite, can be scratched by a penny but not a fingernail. This is due to the Mohs hardness scale, where these minerals have a hardness greater than a penny (3.5) but less than a fingernail (2.5).
Diamond is the hardest mineral and can only be scratched by another diamond.
Between 3.5 and 5.5 on the Mohs scale of mineral hardness.
minearls
The mineral that can be scratched by a penny is talc. Talc is the softest mineral on the Mohs scale, with a hardness of 1. A penny has a hardness of around 3.5 on the Mohs scale.
Mineral that can be scratched with a knife blade or a window glass is gypsum.
topaz
apatite with a steel knife feldspar with window glass
Copper sulfide minerals, such as chalcocite and bornite, can be scratched by a penny but not a fingernail. This is due to the Mohs hardness scale, where these minerals have a hardness greater than a penny (3.5) but less than a fingernail (2.5).
A mineral can be tested for hardness using a fingernail, penny, or nail, which are common items that serve as reference points on the Mohs scale of mineral hardness. For instance, a fingernail has a hardness of about 2.5, while a copper penny is around 3.5. If a mineral can be scratched by a fingernail, it is softer than 2.5; if it can be scratched by a penny but not a fingernail, it falls between 2.5 and 3.5. This simple test helps in identifying the mineral's hardness and assists in classification.
The mineral that can scratch glass but can be scratched by a steel file is quartz. Quartz has a hardness of 7 on the Mohs scale, allowing it to scratch glass, which typically has a hardness of around 5.5. However, a steel file, which has a hardness of about 6.5 to 7, can scratch quartz.
A mineral that can be scratched by a penny (which has a hardness of about 3.5 on the Mohs scale) but not by a fingernail (which has a hardness of about 2.5 to 3) would have a hardness between 3 and 3.5. This means the mineral's hardness is likely around 3.2 to 3.4, indicating it is softer than the penny but harder than a fingernail. Examples of minerals that fit this description could include calcite or gypsum, depending on their specific characteristics.
The mineral you are describing is likely talc. Talc is a nonmetallic mineral that is typically black in some varieties and has a very low hardness of 1 on the Mohs scale, allowing it to be easily scratched by a penny, which has a hardness of about 3. Its softness and slippery feel are characteristic of talc, making it commonly used in products like talcum powder.
It would have to be 5.0 because glass has a hardness of 5.5 and an iron nail has the hardness of 4.5
A mineral with a hardness of 6 on the Mohs scale can be scratched by anything harder than a 6, such as minerals with a hardness of 7 or higher. It will not be scratched by minerals with a hardness of 5 or lower.