<p>I am not a minerals expert, and can't claim expertise on these particular materials. However, from a general physics / materials point of view I'm pretty sure the answer will be that,</p>

<ol>
<li>There is more than enough UV in sunlight to make the minerals fluoresce, but...</li>
<li>The amount of visible light from the fluorescence is low enough to be undetectable by eye on top of the incoming sunlight.</li>
</ol>

<p>It would be easy to test this by putting a black enclosure with a UV-admitting filter over the rocks and an observer's head... :-)</p>

<p>(if anybody with actual specific knowledge would like to confirm or deny this, I'd be very grateful!)</p>

CC BY-SA 3.0
2014-10-20T13:01:04.490Z
This seems reasonable. Even if the minerals glow, you would probably not be able to see it with the naked eye.
Gimelist
CC BY-SA 3.0
2014-10-20T14:31:41.430Z
So, it would definitely be enough to make them "glow in the dark" if you immediately moved it to a dark room?
SuperHuman
CC BY-SA 3.0
2014-10-20T14:33:36.510Z
@SuperHuman ah, that's a slightly different question - you're asking not just about whether the rocks fluoresce enough for the light generated to be seen, but whether they *continue* producing light after the UV source is removed. I'm afraid I don't know the answer to that question.
Semidiurnal Simon
CC BY-SA 3.0
2014-10-20T14:42:17.193Z
Ah, yes, I'm afraid my question might have been a little misleading. Thank you for the effort.
SuperHuman
CC BY-SA 3.0
2014-10-20T12:31:14.360Z
2015-01-23T11:40:36.520Z
2015-01-23T11:40:36.520Z
Semidiurnal Simon
<p>The lifetime of a fluorescence excited state is on the nanosecond to microsecond time scale.  So once the excitation source light is removed, the emission of light will stop within microseconds. </p>

<p>Note that <a href="http://en.wikipedia.org/wiki/Fluorescence">fluorescence</a> is distinct from <a href="http://en.wikipedia.org/wiki/Phosphorescence">phosphoresence</a>, and phosphorescence can involve longer lifetime excited states.</p>

<p><a href="http://pubs.acs.org/doi/pdf/10.1021/es049417l">Spectroscopic Characterization of the Uranium Carbonate Andersonite</a> provides quantitative information on fluorescence lifetimes for Andersonite, and lifetimes are in the microsecond range.  </p>

<p>Regarding phosphorescence, see <a href="https://archive.org/details/phosphorescenceo00phip">Phosphorescence; or, The emission of light by minerals, plants, and animals (1862)</a>:</p>

<blockquote>
  <p>SEVERAL substances manifest the strange property  of emitting light
  when they are placed in darkness,  after having been exposed for some
  time to the  direct rays of the sun. In some cases a very short 
  exposure to sunlight is sufficient to excite the  manifestation of
  this remarkable property, and in  others the direct rays of the sun
  are not necessary :  it suffices that the substance experimented upon 
  be exposed to the dull light of a cloudy day. To  this phenomenon the
  denomination of Phosphores-  cence after insolation has been given. </p>
  
  <p>' The substances which possess this property in  the highest degree
  are the Bologna stone, or solar  phosphorus, certain varieties of
  fluor-spar and  carbonate of lime, some fossils, calcined shells or 
  pearls, phosphate of lime, arseniate of lime, etc.  Many diamonds
  shine with brilliancy in the dark  if they have previously undergone
  an exposure of  some seconds' duration only to solar light. But  no
  substance surpasses in this respect sulphuret  of barium. </p>
  
  <p>It is now a long time since the cobbler of Bologna,,  in Italy,
  astonished and amused his friends with a  peculiar substance since
  known as Bologna phosphorus, Bologna stone, or Solar phosphorus,
  which  shines brightly in the dark after having been placed  in the
  sunlight for some time. This substance is  sulphuret of barium. The
  cobbler prepared it by  heating red-hot with charcoal a piece of
  sulphate  of baryta, or Barytine, (Fig. I,) a stone which he...</p>
</blockquote>

CC BY-SA 3.0
2014-10-20T19:59:47.240Z
Ah, seems I was looking for Phosphorescent materials...
SuperHuman
CC BY-SA 3.0
2014-10-21T14:53:18.417Z
ok, I added a reference to answer that answers your question, but for phosphorescence
DavePhD
CC BY-SA 3.0
2014-10-20T17:35:32.953Z
2014-10-22T11:12:37.067Z
2014-10-22T11:12:37.067Z
DavePhD
<p>I have been searching certain fluorescent minerals, such as Andersonite, and all websites are saying how the mineral will glow if exposed to Ultraviolet light. Does enough ultraviolet light come through the atmosphere (from the sun), to make any natural minerals actually glow, and to keep glowing for a time if the light was removed? If there is not enough UV light, or if no such mineral exists, would it be possible for such a mineral to exist?</p>

<atmosphere><minerals>
Is it possible for a natural fluorescent mineral to glow from the sun's rays?
SuperHuman
# Is it possible for a natural fluorescent mineral to glow from the sun's rays?

(Asked by: username_0 on 2014-10-20)

I have been searching certain fluorescent minerals, such as Andersonite, and all websites are saying how the mineral will glow if exposed to Ultraviolet light. Does enough ultraviolet light come through the atmosphere (from the sun), to make any natural minerals actually glow, and to keep glowing for a time if the light was removed? If there is not enough UV light, or if no such mineral exists, would it be possible for such a mineral to exist?

**Tags:** atmosphere, minerals


---

## 2 answers

### Answer by username_3 on 2014-10-20. Score: 9 | Accepted answer

The lifetime of a fluorescence excited state is on the nanosecond to microsecond time scale. So once the excitation source light is removed, the emission of light will stop within microseconds.

Note that [fluorescence](http://en.wikipedia.org/wiki/Fluorescence) is distinct from [phosphoresence](http://en.wikipedia.org/wiki/Phosphorescence), and phosphorescence can involve longer lifetime excited states.

[Spectroscopic Characterization of the Uranium Carbonate Andersonite](http://pubs.acs.org/doi/pdf/10.1021/es049417l) provides quantitative information on fluorescence lifetimes for Andersonite, and lifetimes are in the microsecond range.

Regarding phosphorescence, see [Phosphorescence; or, The emission of light by minerals, plants, and animals (1862)](https://archive.org/details/phosphorescenceo00phip):

> SEVERAL substances manifest the strange property of emitting light
> when they are placed in darkness, after having been exposed for some
> time to the direct rays of the sun. In some cases a very short
> exposure to sunlight is sufficient to excite the manifestation of
> this remarkable property, and in others the direct rays of the sun
> are not necessary : it suffices that the substance experimented upon
> be exposed to the dull light of a cloudy day. To this phenomenon the
> denomination of Phosphores- cence after insolation has been given.
>
> ' The substances which possess this property in the highest degree
> are the Bologna stone, or solar phosphorus, certain varieties of
> fluor-spar and carbonate of lime, some fossils, calcined shells or
> pearls, phosphate of lime, arseniate of lime, etc. Many diamonds
> shine with brilliancy in the dark if they have previously undergone
> an exposure of some seconds' duration only to solar light. But no
> substance surpasses in this respect sulphuret of barium.
>
> It is now a long time since the cobbler of Bologna,, in Italy,
> astonished and amused his friends with a peculiar substance since
> known as Bologna phosphorus, Bologna stone, or Solar phosphorus,
> which shines brightly in the dark after having been placed in the
> sunlight for some time. This substance is sulphuret of barium. The
> cobbler prepared it by heating red-hot with charcoal a piece of
> sulphate of baryta, or Barytine, (Fig. I,) a stone which he...

> **Comments:**
> **username_0**: Ah, seems I was looking for Phosphorescent materials...  
> **username_3**: ok, I added a reference to answer that answers your question, but for phosphorescence  

---

### Answer by username_1 on 2014-10-20. Score: 7

I am not a minerals expert, and can't claim expertise on these particular materials. However, from a general physics / materials point of view I'm pretty sure the answer will be that,

1. There is more than enough UV in sunlight to make the minerals fluoresce, but...
2. The amount of visible light from the fluorescence is low enough to be undetectable by eye on top of the incoming sunlight.

It would be easy to test this by putting a black enclosure with a UV-admitting filter over the rocks and an observer's head... :-)

(if anybody with actual specific knowledge would like to confirm or deny this, I'd be very grateful!)

> **Comments:**
> **username_2**: This seems reasonable. Even if the minerals glow, you would probably not be able to see it with the naked eye.  
> **username_0**: So, it would definitely be enough to make them "glow in the dark" if you immediately moved it to a dark room?  
> **username_1**: @username_0 ah, that's a slightly different question - you're asking not just about whether the rocks fluoresce enough for the light generated to be seen, but whether they *continue* producing light after the UV source is removed. I'm afraid I don't know the answer to that question.  
> **username_0**: Ah, yes, I'm afraid my question might have been a little misleading. Thank you for the effort.  

---

