It means you have injured a fingernail.
Ad unguem means to the fingernail, to a nicety, exactly.
Marginally. Halite has a hardness of 2 to 2.5, about the same as a fingernail.
Hornblende is a mineral with a hardness of about 5 to 6 on the Mohs scale, which means it is harder than a fingernail, which has a hardness of about 2.5 to 3. Therefore, hornblende cannot be scratched by a fingernail. Instead, a fingernail would likely be scratched by hornblende if they came into contact.
Ad unguem means to the fingernail, to a nicety, exactly.
No, emeralds are relatively hard gemstones, ranking 7.5-8 on the Mohs scale of mineral hardness, while a fingernail ranks around 2-2.5. This means that an emerald should not be easily scratched by a fingernail.
Talc is a very soft mineral, ranking as 1 on the Mohs scale of hardness, and your fingernail is harder at around 2.5. This means your fingernail can easily scratch talc due to the difference in hardness levels.
The length of your index fingernail
A centimeter is about the width of a fingernail
The length of your index fingernail
Ongle is fingernail in French.
Onycho- is the prefix pertaining to the fingernail.