# Azure Asterism (DD-166)

> Sapphire is gem corundum, aluminum oxide, in any color except red, which is called ruby. Blue sapphire gets its color from iron and titanium, and sapphires also come in pink, yellow, green and colorless forms. Some sapphires show asterism, a six-rayed star caused by light reflecting off needle-like rutile inclusions. The Star of India is a 563-carat grayish-blue star sapphire held by the American Museum of Natural History in New York, and it is unusual for being nearly free of flaws. The footage shows blue and fancy sapphires and the Star of India, with the presenter.

- Department: Science
- First published: 2024-01-07
- Last updated: 2024-01-07
- Permalink: https://detailenjoyer.com/case/azure-asterism/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-166-F01**: Sapphire is gem corundum. _(Write-up · Exhibit A (Corundum))_
- **DD-166-F02**: Iron and titanium make it blue. _(Write-up · Exhibit B (Iron and titanium))_

## Write-up

Needle inclusions give star sapphires their star. The Star of India weighs about 563 carats.

1. **Corundum**: Sapphire is gem corundum.
2. **Iron and titanium**: Iron and titanium make it blue.
3. **Many colors**: Sapphires come in many colors.
4. **Asterism**: Rutile needles make a six-rayed star.
5. **Star of India**: The Star of India is 563 carats.

## Related case files

- [Ruby Red (DD-167)](https://detailenjoyer.com/case/ruby-red/): I linked ruby, the red form of corundum
- [Shine Bright (DD-165)](https://detailenjoyer.com/case/shine-bright/): I linked the gem the Reel compared it to

## Reel vs. record

- **Note**: 'Sapphires, like diamonds, belong to the corundum mineral family': diamonds are carbon, not corundum.

## Video: Azure Asterism: Needle Inclusions Give Star Sapphires Their Star

- Duration: 30.0 s · Published: 2024-01-07
- File: https://detailenjoyer.com/assets/videos/C1yfpfWsYaj.mp4

### Transcript

Sapphires like diamonds belong to the corundum mineral family and are primarily composed of aluminum oxide. DID YOU KNOW? What distinguishes sapphires is their vibrant range of colors with blue being the most well-known. However, sapphires can also be found in various hues such as pink, yellow, green, and even colorless. One of the most famous sapphires is the Star of India which is a massive nearly flawless blue sapphire. This gem exhibits a unique asterism a star-like pattern that emerges when light reflects off needle-like inclusions in the stone. NOW YOU KNOW!

## Questions & answers

**Q: What mineral is sapphire?**  
A: Aluminum oxide. _(Source: Write-up · Exhibit A (Corundum) · Wikipedia: Sapphire)_

**Q: What is red corundum called?**  
A: Not sapphire. _(Source: Write-up · Exhibit B (Iron and titanium) · Wikipedia: Sapphire)_

**Q: What makes blue sapphire blue?**  
A: Trace elements. _(Source: Write-up · Exhibit C (Many colors) · Wikipedia: Sapphire)_

**Q: What causes asterism?**  
A: Rutile needles. _(Source: Write-up · Exhibit D (Asterism) · Wikipedia: Sapphire)_

**Q: Where is the Star of India?**  
A: In New York. _(Source: Write-up · Exhibit E (Star of India) · Wikipedia: Star of India (gem))_

## Sources

- [Wikipedia: Sapphire](https://en.wikipedia.org/wiki/Sapphire)
- [Wikipedia: Star of India (gem)](https://en.wikipedia.org/wiki/Star_of_India_(gem))

## Cite this case file

Easterling, Marcus. "Azure Asterism." The Detail Department (DetailEnjoyer), case file DD-166, last updated Jan 7, 2024. https://detailenjoyer.com/case/azure-asterism/