The answer is "They fracture." When struck with a rock hammer, minerals like quartz, obsidian, and hematite, fracture or break at random directions instead of along cleavage planes at consistent angles. This means that these minerals have no mineral cleavage and exhibit conchoidal or irregular fractures.
Scientists finally found the reason for the periodicity of the elements: Valence electrons. And so the table became known as the Periodic Table
<span>This family of elements is headed by boron. In this case, atomic size increases as one goes down the periodic table, as there are more electrons in each successive element needed to fill the outer shells. As such, thallium, at the lowest level of the group 3a column, will have the largest atomic size.</span>
It does not affect the melting point but it might affect your ability to see the melting point