In response to yet another frame materials question, I thought it might be useful to start with a more answerable question. One answer per material please, with an example of a bicycle frame using that material.

Please use the format I've used in my answer(s) to make it easy to compare materials.

I see no harm in having all 400+ steel alloys listed if someone wants to do that, but "steel" must specifically be low-grade mild steel rather than a specific alloy. Likewise for aluminium, titanium, magnesium and other metals.

For composites, including metal composites, I would again prefer specific examples with details (there's a big difference between steel reinforced concrete and kevlar/polyester composites). I would also love to see weird and wonderful bikes included.

## Materials 

(ie index to answers. Please update links as you add an answer):

### Metals
 
 - **Aluminum Bikes**
    - **[Aluminum](https://bicycles.stackexchange.com/a/58015/26330)**
    - **[Scandium](https://bicycles.stackexchange.com/questions/43838/what-different-frame-materials-have-been-used/44545#44545)** - Aluminium alloy
 - **Steel Bikes**  
    - **Columbus Steel**  (not written yet)  
    - **ChromeMoly Steel** (not written yet)  
    - **[Gaspipe Steel](https://bicycles.stackexchange.com/a/45078/19705)**
    - **Ishiwata Steel**  (not written yet)  
    - **Kaisei Steel**  (not written yet)  
    - **[Mild Steel](https://bicycles.stackexchange.com/a/43839/8273)**  
    - **[Reynolds Steel](https://bicycles.stackexchange.com/a/45082/19705)** (needs extension)
    - **Tange Steel**  (not written yet)  
    - **Vitus/Super Vitus Steel**  (not written yet)  
 - **[Titanium](https://bicycles.stackexchange.com/a/44493/19705)**
 - **[Beryllium](https://bicycles.stackexchange.com/a/57625/26330)**
 - **[Gold (pure)](https://bicycles.stackexchange.com/a/43845/19705)**  (theoretical)
 - **[Magnesium](https://bicycles.stackexchange.com/a/92201/54500)** (needs extension)

### Organic
 - **[Bamboo](https://bicycles.stackexchange.com/a/44989/31280)**
 - **[Bones](https://bicycles.stackexchange.com/a/43849/19705)**
 - **Wood Bikes**
    - **[Carved Wood](https://bicycles.stackexchange.com/a/44550/19705)**
    - **[Plywood](https://bicycles.stackexchange.com/a/43842/7044)** (composite)  
    - **[Wood](https://bicycles.stackexchange.com/a/43843/7044)** (complete frame and bicycle)
 - **Cardboard** (not yet written)

### Composites and Polymers
 - **[Carbon Fibre](https://bicycles.stackexchange.com/a/43854/13174)**  
 - **[Flax fiber (90% flax, 10% carbon)](https://bicycles.stackexchange.com/a/44582/26330)**
 - **[Plastic]( https://bicycles.stackexchange.com/a/57627/35081)**
 - **[Ceramic/Aluminium](https://bicycles.stackexchange.com/a/92197/19705)**

### Layout Specific
 - **[Cables](https://bicycles.stackexchange.com/a/43847/19705)** aka Tensegrity or Tensional Integrity
 - **[3D Printed](https://bicycles.stackexchange.com/a/43848/19705)** (not yet written)