Home >> Science & Nature >> Rocks & Minerals

How to Identify Tungsten Ore

Tungsten is an element. It its pure form, it is a soft light grey or whitish metal. It has a number of practical uses, both in its pure form and as an alloy. However, tungsten is typically not found in pure form; it is instead processed from minerals, usually wolframite or scheelite. Although making a completely positive identification of a mineral is difficult without professional experience, these particular minerals have many properties that anyone can examine to determine whether a specimen is likely one of them.

Things You'll Need

Streak plate
Steel nail
UV light
Hydrochloric acid
Magnet

Instructions

- 1
  Examine the mineral. Wolframite ranges from black or greyish black to brown, is opaque and is slightly metallic. Scheelite is more varied; it can be tan to dark brown, golden to pale yellow, brownish yellow, reddish yellow, greenish, colorless or white. Its crystals can be transparent or opaque, and they have a shiny or glassy appearance.
- 2
  Rub the mineral against a streak plate, a piece of plain white unglazed porcelain. Wolframite leaves a reddish brown color on a streak plate. Scheelite makes a white streak, which may be difficult to see.
- 3
  Scratch the mineral with the steel nail, which has a Mohs hardness of about 5. (The Mohs scale measures the hardness of minerals relative to one another.) Wolframite and sheelite each have a Mohs hardness of 4.5, so the nail will leave a mark on either.
- 4
  Examine the other minerals that may have formed on your specimen. Wolframite often develops with topaz and quartz. Scheelite often develops with tremolite, tourmaline, topaz, vesuvianite, cassiterite, fluorite, diopside and apatite. In addition, wolframite and scheelite are often found together.
- 5
  Measure the crystal's specific gravity -- its weight in comparison with its volume. This measurement can be taken in many ways, but all require special equipment or calculations for accuracy. However, this is a good way to identify minerals. The specific gravity of wolframite is 7.40 grams per cubic centimeter. The specific gravity of scheelite is 6.01 grams per cubic centimeter. If you do not have access to such equipment, heft the sample in your palm. Both minerals should feel fairly heavy for their size.
- 6
  Place a magnet on a mineral thought to be wolframite. Wolframite contains iron, making it slightly metallic.
- 7
  Shine a UV light on a mineral thought to be scheelite. Scheelite fluoresces bright white-blue under a UV light if it is very pure, and creamy yellow if it contains molybdenum.
- 8
  Drip a small amount of diluted hydrochloric acid on the specimen. If it is scheelite, the acid will decompose it into a yellow powder.

Rocks & Minerals