MINERAL FAMILIES

"Mineral families....I have an Aunt Amythyst and an Uncle Rocko, but I guess that's not what you mean...!"
"Keerect, Lou! That's not what I mean! I'm talking about minerals that have their atoms arranged in the same way and have almost the same compositions! The result is you get minerals that have a strong resemblance and differ only in minor ways - like a family! Take a look below at the Feldspar and the Mica Families!"
"The Feldspar Family has lots of members! I've only shown a few! They're all made of a constant component (aluminum plus silicon plus oxygen) plus a variable component (either potassium and/or sodium and/or calcium)! In the schematic diagrams, the constant component is represented by black dots; the variable component is represented by colored dots!"
"You can see the pattern is the same for each member! And the composition is almost the same! What varies is the hue of the colored dots! Red for potassium; green for sodium; blue for calcium! Notice that one member has a mixture of green and blue! The result is that all the members of the Feldspar Family strongly resemble each other physically and chemically: they're all hard to scratch, break in a 'blocky' fashion, have similar density, are difficult to dissolve.... But may differ in their color and other features!"
"And here's the Mica Family! Both biotite and muscovite break into flat, flaky pieces, and have other properties in common! But due to a small, but significant difference in one of the chemical components, their colors and electrical conductivity vary!"
"They're kind of attractive! In a subtle way!!"
"They are, Lou, they are!!"

2010, Michelle O'Dea