An unknown mineral scratches apatite and is scratched by corundum. what can you conclude about this mineral’s hardness?

If we guide ourselves with the Moh´s scale:

Material scratches apatite → material is harder than 5.

Material is scratched by corundum → material is softer than 9.

Conclusion:

The hardness of the unknown material stands between 5 and 9.

Note:  

Both apatite and corundum are defining materials (reference materials in the Moh´s scale). So, you can also give an answer using defining materials:

"It can either be an orthoclase feldspar, a quartz or a topaz".

Hope it helped,

BiologiaMagister

This answer is dedicated to JaySL

typically, most spiders possess eight eyes. however, others have as many as 12, and some don't have any. these eyes are for detecting light from dark, deciphering shapes and for gathering their prey.

image result for describe the various types of gene mutationsghr.nlm.nih.gov

the types of mutations include: missense mutation: this type of mutation is a change in one dna base pair that results in the substitution of one amino acid for another in the protein made by a gene. nonsense mutation: a nonsense mutation is also a change in one dna base pair.

explanation: