Isomorphism

Isomorphic Materials

Materials that can contain ALTERNATIVE ATOMS within the SAME basic crystal structure

Isomorphic Replacement

- Replacement of 1 chemical element by another in a crystalline material

- crystal structure stays the same but physical properties vary

Isomorphism

minerals exhibit isomorphism when then have identical external forms but differ chemically

4 Isomorphic groups

1. Garnet Group
2. Feldspar Group
3. Olivine Group
4. Tourmaline

2 groups in garnet family

1. Pyralspite
2. Ugrandite

3 garnet species in the Pyralspite Group

1. Pyrope
2. Almandine
3. Spessartine

- "Pyr" = greek for fire!
- Aluminum garnets

3 garnet species in the Ugrandite Group

1. Uvarovite
2. Grossular
3. Andradite

- Calcium garnets!

Pyralspite Group physical properties

- pure red to orange-red colours
- "Pyr" = greek for fire!
- Aluminum garnets (Al as Y element)

Ugrandite Group physical properties

- brown, yellow, green colous
- Calcium garnets! (Ca as X element)

2 Feldspar Families

1. Alkali Feldspar
2. Plagioclase Feldspar

Distinguishing Element in Alkali Feldspar

Potassium (K)

- potassium added into chemical formula of these stones

3 feldspar species in Alkali Feldspar Family

1. Anorthoclase
2. Sanidine/ Orthoclase, Moonstone
3. Microline Amazonite

6 feldspar species in Plagioclase Feldspar Family

1. Albite
2. Oligoclase
3. Andesine
4. Labradorite
5. Bytownite
6. Anorthite

2 species in Olivine Group

1. Forsterite
2. Fayalite