Properly ventilating a deep mine is a significant engineering challenge. Ergo, you don't want to be carrying around torches that use up some of your precious breathing oxygen if you don't absolutely have to.

So, suppose we have a civilization of dwarves that have all learned to use echolocation (like many actual blind people do) to get around efficiently in total darkness. Now they don't need torches, which helps keep their mines cooler and the air more wholesome. But, they can no longer see the color of the rocks and minerals they are digging up--at least, not until they take a sample back to the surface.

So, what methods are there to safely (i.e., "lick it!" should not be the first resort) identify what a dwarven miner is digging up in the dark?

  • $\begingroup$ Colour is only one of very many factors used to identify minerals. What kind of texture resolution is their echolocation capable of? $\endgroup$ Aug 23, 2019 at 1:26
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    $\begingroup$ Any junior mine geologist will tell you that that colour is the most misleading things to look for when looking for ore. In the old days it's a combination of colour, texture, smell (for examples, when hitting sulfides), the reactivity of the mineral to various acids, etc. $\endgroup$
    – Gimelist
    Aug 23, 2019 at 1:33
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    $\begingroup$ I had the perfect answer until you said '"lick it!" should not be the first resort'. $\endgroup$ Aug 23, 2019 at 1:55
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    $\begingroup$ Or use a canary, smithsonianmag.com/smart-news/… The small birds would die before poisonous gases built up to levels dangerous to miners. $\endgroup$
    – Sarriesfan
    Aug 23, 2019 at 17:19
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    $\begingroup$ See: google.com/amp/s/www.sciencealert.com/…. Human eyes also contain cry4. Consider the selective pressure on Dwarves, well for a start the're Dwarves, if their body type is a result of selective pressure then how much more advantageous would a magnetic sense be? You could flip the effect of light - less light increases the effect. In addition the Wikipedia article on Magnetoception provides a couple of articles that suggest some mammals, including bats, ruminants and canids may have this sense. $\endgroup$
    – pHred
    Aug 24, 2019 at 13:41

4 Answers 4


Miners working gold mines in the California gold rush conserved expensive candles by striking their iron tools against the rock walls and throwing sparks. It gave them enough light to navigate and see where the gold bearing quartz veins were.

So dwarves might use the same technique.

They could also carry different touchstones to test the ores. The term touchstone comes from a type of mineral that could be used to test if a gold coin was genuine. Maybe the dwarves have many different stones and ceramics that turn different colors when marked or scraped against a stone containing an ore.

Similarly to the iron tools being used for throwing sparks, maybe they have specialized flint and steels that throw different color sparks.

Putting these two together, a combination of touchstones and sparkers might be used to assess type and quality of ore they find digging in the earth.


Take a page from people who mine gold out of riverbeds in poor countries.

Your dwarves put the ores inside a bucket filled with mercury. Gold, silver, zync and other metals amalgamate with the mercury, resulting in a liquid alloy from which you can easily remove the more precious metals later on a lab. Meanwhile the impurities don't mix with the mercury. If you've ever seen liquid mercury, you know how easy it is to separate from the impurities.

So dig away, and bring just the buckets full of liquid alloy home later.

And if anyone tells you that quicksilver is bad for your health, remember, dwarves have undergone natural selection under the mountains. They should be very tolerant to it.


Weight and Texture

Even now we use the specific gravity of a material to determine it's make up.

See Clyde Pulp Density Scales

Now a blind dwarf should be able to feel any crystal structures as well as the weight of the material to know the type and quality of the ore

In a pinch smell could also factor in. When a person is blind, the other senses are heightened.


Nonvisual properties, such as conductivity, specific heat, specific gravity, density, texture, magneticity, etc.

You can probably tell identical gold-plated / silver-plated mugs apart by touch, because there will be less gold, and the gold one will be lighter. If you have identical gold / silver lumps, the gold will be heavier, because gold is more dense and natural lumps don't care about saving money on production. Two cups, one filled with water, and the other with orange juice, will feel different when grasped, if they start at the same temperature, because they will change temperatures at different rates. The same can apply to minerals: given two crystals with different thermal properties, you can tell them apart by holding one in each hand, and feeling which changes temperature fastest, and how quickly it reaches the new equillibrium. If you're dealing with loose particles and dusts, consider how different minerals react to static electricity. The simplest demonstration of this is to charge a balloon or sheet of plastic or whathaveyou, and move it over a mix of salt and pepper. One should be lifted due to the charge difference, and the other is left behind.

The limits depend on the available technology, or if visual sorting post-collecting is an option. I would assume that cupric rocks will respond differently to an electric current than other random rocks of similar texture, but I don't know the details, having only really heard about identifying copper ores by color. The examples I gave might be difficult to distinguish without finer measurements than human-like senses can perceive, for certain minerals.


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