What controls the ability of an element to substitute for another one in a mineral?

What controls the ability of an element to substitute for another one in a mineral?

The factors that control the amount of solid solution that can take place in any given crystal structure are: The size of the ions and the size of the crystallographic sites into which they substitute.

What factors are required for element substitution?

Ions of two different elements can freely replace one another only if their ionic radii differ by approximately 15 percent or less. Limited substitution can occur if the radii differ by 15 to 30 percent, and a difference of more than 30 percent makes substitution unlikely.

What properties must be similar for atoms to substitute for one another?

Different atoms may have similar ionic radii and when they do, they can easily substitute for each other in a crystal structure. Ionic substitution is possible when the ionic radii is not too different. The over charge of a substitution can be different if the structure allows for compensation.

What is substitution of an element?

Substitution groups are very similar to choice types. They allow a given base element (referred to as the substitution group head) to be replaced with a different element.

What are three different ways minerals can form?

The four main categories of mineral formation are: (1) igneous, or magmatic, in which minerals crystallize from a melt, (2) sedimentary, in which minerals are the result of sedimentation, a process whose raw materials are particles from other rocks that have undergone weathering or erosion, (3) metamorphic, in which …

What controls a mineral’s color?

The atomic bonds within a mineral generally determine which wavelengths of light will be absorbed and which will be reflected. Those wavelengths that are reflected back to our eyes determine the color of the mineral. Some minerals have free electrons that will absorb certain wavelengths of light.

What is Goldschmidt’s rule?

GOLDSCHMIDT’S RULES. 1. The ions of one element can extensively replace those of another in ionic crystals if their radii differ by less than approximately 15%. 2. Ions whose charges differ by one unit substitute readily for one another provided electrical neutrality of the crystal is maintained.

What is the difference between atoms compounds and minerals?

Just as chemical elements are made up of atoms, a chemical compound is made up of molecules. Each molecule in a chemical compound is made up of two or more different atoms connected together. The atoms in a mineral are arranged in an organised ‘atomic structure’.

What is a solid solution series?

A solid solution series is the compositional range between end-member minerals that share the same basic chemical formula but experience substitution of elements in one or more atomic sites. For example, iron and magnesium can readily replace one another in a mineral.

How crystals are formed?

How are crystals formed? Crystals form in nature when molecules gather to stabilize when liquid starts to cool and harden. This process is called crystallization and can happen when magma hardens or when water evaporates from a natural mixture too. This is how crystals are formed in nature.

What is atomic substitution?

When the chemical composition of a mineral varies because of atomic substitution, the mineral is said to exhibit “Solid Solution” Solid Solution is defined as “a mineral structure in which specific atomic site(s) are occupied in variable proportions by two or more different elements.” (

Why is solid solution by ionic substitution so common in nature?

Ionic substitution – (also called solid solution), occurs because some elements (ions) have the same size and charge, and can thus substitute for one another in a crystal structure.

What are the different types of plagioclase feldspars?

The plagioclase feldspars are named according to the following scheme, where the numbers are the percentage of calcium expressed as anorthite (An): 1 Albite (An 0–10) 2 Oligoclase (An 10–30) 3 Andesine (An 30–50) 4 Labradorite (An 50–70) 5 Bytownite (An 70–90) 6 Anorthite (An 90–100) More

What makes potassium feldspar different from other minerals?

The formula actually is a blend ranging from all sodium (albite) to all potassium (microcline), but albite is also one endpoint in the plagioclase series so we classify it there. This mineral is often called potassium feldspar or K-feldspar because potassium always exceeds sodium in its formula.

Which is the correct formula for alkali feldspar?

Alkali Feldspar in Detail Alkali feldspar has the formula KAlSi 3 O 8, potassium aluminosilicate. The formula actually is a blend ranging from all sodium (albite) to all potassium (microcline), but albite is also one endpoint in the plagioclase series so we classify it there.

Which is a softer mineral quartz or feldspar?

Feldspar is called a rock-forming mineral, very common, and usually makes up a large part of the rock. In sum, any glassy mineral that’s slightly softer than quartz is very likely considered a feldspar. The main mineral that might be confused with feldspar is quartz.