# what is mineral glass?



## ZippyDan (Dec 13, 2006)

also called sapphire glass i believe?

i wikipedia'd and cpfwiki'd for both and found nothing.

im wondering what it is made of/how it is made/benefits of this

whoever answers my question should make a wikipedia article about it


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## PhotonFanatic (Dec 13, 2006)

Well sapphire lenses, or windows, are made specifically from sapphire and is a type of "mineral", i.e., it contains aluminum oxide.

Mineral glass is also known as opthalmic glass. 

Here is a little blurb that should be of interest:

_Mineral Lenses_
_Manufacturing_
_Glass ingredients_

_Pure silica (SiO2) has a melting point of about 2000 °C (3600 °F), and while it can be made into glass for special applications (see fused quartz), two other substances are always added to common glass to simplify processing. One is soda (sodium carbonate Na2CO3), or potash, the equivalent potassium compound, which lowers the melting point to about 1000 °C (1800 °F). However, the soda makes the glass water-soluble, which is usually undesirable, so lime (calcium oxide, CaO) is the third component, added to restore insolubility. The resulting glass contains about 70% silica and is called a soda-lime glass. Soda-lime glasses account for about 90% of manufactured glass._

_As well as soda and lime, most common glass has other ingredients added to change its properties. Lead glass, such as lead crystal or flint glass, is more 'brilliant' because the increased refractive index causes noticeably more "sparkles", while boron may be added to change the thermal and electrical properties, as in Pyrex. Adding barium also increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion, and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern glasses. Large amounts of iron are used in glass that absorbs infrared energy, such as heat absorbing filters for movie projectors, while cerium(IV) oxide can be used for glass that absorbs UV wavelengths (biologically damaging ionizing radiation)._

_Glasses that do not include silica as a major constituent are sometimes used for fibre optics and other specialized technical applications. These include fluorozirconate, fluoroaluminate, and chalcogenide glasses. _

As you can see, the addition of certain minerals changes the properties considerably. For more info see this.


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## David_Campen (Dec 13, 2006)

I believe it is a very general term. It could be soda lime glass (silica and sodium carbonate) or any of the more complex formulations of various inorganic oxides. It is used to distinguish a glass made of inorganic oxides from other things. 

The term glass can mean many things - for example a plastic window might be referred to as a glass. Specifying "mineral" glass would exclude plastic.

Sapphire is not a glass, it is a crystal. So a sapphire window would not be a mineral glass window.


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## FirstDsent (Dec 14, 2006)

Synthetic sapphire doesn't contain aluminum oxide, it _is_ aluminum oxide. It is pure aluminum oxide. The presence of trace minerals like titanium (blue sapphire) and chromium (ruby) give aluminum oxide its gem colors. Pure aluminum oxide is clear and is the second hardest substance next to diamond. I'm not sure about its light transmission properties. It is just described as "excellent light transmission" -that is surely subjective.

Bernie


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## PhotonFanatic (Dec 14, 2006)

I stand corrected on the composition of synthetic sapphire windows.

The transmission is OK for 2mm thick windows, but not great:


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## LowTEC (Dec 16, 2006)

So in other words, when flashlight manufacturers use the term "mineral glass" basically means that it _is_ glass, not plastic?


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## UncleFester (Dec 16, 2006)

Hmmm.... What is mineral glass.. I dunno, but I wonder if you are supposed to clean it with mineral water or are you supposed to use mineral spirits.


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## greenLED (Dec 16, 2006)

Coming to a flashlight near you...


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## NewBie (Dec 16, 2006)

An example for comparison sakes to 2 sided AR glass:






Mineral glass is tougher.


A comparision of uncoated window materials:


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## David_Campen (Dec 17, 2006)

LowTEC said:


> So in other words, when flashlight manufacturers use the term "mineral glass" basically means that it _is_ glass, not plastic?


Yes.


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## carbine15 (Dec 17, 2006)

greenLED said:


> Coming to a flashlight near you...


Life imitates art imitates life.:rock:


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## vortechs (Dec 17, 2006)

In addition to all the good information here about "mineral glass" and clear sapphire, I'd also be interested in additional information about Borofloat or UCL "lenses" (or windows, if you prefer that term). 

According to FlashlightLens.com the Borofloat lens is borosilicate (which is similar to Pyrex). Its advantage is its ability to withstand high temperatures and thermal shocks better than other types of glass, which makes it good for 'hotwire' incandescent mods. 

I'm not sure what the UCL lenses are made of, but I remember that the name "UCL" belongs to the folks at FlashlightLens.com.


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## pcmike (Feb 21, 2007)

Someone care to shed some light on what exactly UCL is? I'm interested as well. Where exactly does it fit into the graphs Newbie posted?


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## benighted (Feb 21, 2007)

greenLED said:


> Coming to a flashlight near you...


 
"Mr. Computer?"
Meh, I guess we still need the keyboard :sigh:


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## bombelman (Feb 21, 2007)

Also, where does LEXAN come in ?


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## lukus (Feb 22, 2007)

I think UCL stands for Ultra Clear Lens. Don't remember my source though.


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## Scott Packard (Feb 28, 2007)

The ALON Optical Ceramic (transparent aluminum) looks pretty good too.
http://www.surmet.com/alon.html
Similar transmittance to sapphire, should be very resistant to scratches.


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