Hornblende is the name used to describe Magnesio-hornblende and Ferro-hornblende. However, the term is generally more inclusive for all calcium-aluminum amphiboles. The name Hornblende is frequently used to describe any dark, opaque Amphibole mineral without any individual analysis.
The varieties of Hornblende look incredibly similar and can be nearly indistinguishable without complex analysis.
This mineral is a significant component of the Earth and is incredibly common. It forms in a variety of mineral environments and is often a substantial constituent of the rock types it forms in.
This mineral is named after the German term horn, in reference to its color and blenden, meaning ‘deceiver,’ alluding to Hornblende’s habit of being confused with ore metals because of its luster and dark colors.
Hornblende Physical Properties
Hornblende is a darker stone or mineral that can be found in various hues, including black, dark grey, dark green, and dark brown. However, lighter colors can be found in the extended Hornblende family, which includes members such as Pargasite and Edenite.
Hornblende has a hardness between 5 to 6 on the Mohs Hardness Scale and produces a colorless streak. Its crystal system is monoclinic, and it forms as tabular or prismatic crystals with a diamond-shaped cross-section. It’s rarely found in individual crystals and is almost always in dense groups of grainy or platy crystals. Hornbelend can also be found in columnar, radiating, fibrous, acicular aggregates and veins.
Hornblende has opaque transparency, but it may be slightly translucent on thin cross-sections under strong black-lighting. The luster of this stone can be vitreous, submetallic, or dull. Its cleavage is prismatic, and the fracture is uneven or splintery.
Is Hornblende Magnetic?
Hornblende is actually paramagnetic which means it s very weakly attracted by the poles of a magnet, but it doesn’t retain any permanent magnetism.
Paramagnetism, simply put, is the magnetic state of an atom containing one or more unpaired electrons.
Hornblende rates a 6 on the Mohs Hardness Scale.
Hornblende Streak Test
A mineral or stone’s streak is simply the color of the mineral powder. Many minerals have a different color when in powdered form than they do in massive or crystal structures. The color can be entirely separate or a different shade. Several minerals produce a powder streak that’s lighter in color than the whole crystal. While some produce no color at all.
Hornblende produces a colorless streak.
You see, a streak is typically obtained by dragging a sharp edge, point, or grain of a crystal across a streak plate. These plates are simply unglazed pieces of porcelain tile, like those used in bathrooms and kitchens.
Porcelain streak plates have a relative hardness of about 6.5, so minerals of that hardness or greater can’t be tested on it because they will only scratch the plate. Some geologists and gemologists use a steel file to test the streak of minerals with a hardness of 6 to 6.5.
Some minerals are difficult to get a good powdered streak from. As with any test, repetition usually pays off in the end. You need to use a sharp edge or points instead of simply dragging the mineral across the streak plate. While some soft minerals produce a streak easily, regardless of how we drag them, others won’t streak well unless we use a small surface area of the mineral.
That said, if you conduct a streak test and the specimen doesn’t produce a streak after several tries, you’re dealing with something with a hardness of 6 to 6.5 or higher.
Hornblende is a dark-colored stone or mineral ranging from black, dark brown, dark green, and dark grey.
Hornblende Specific Gravity
Hornblende has a specific gravity between 3.0 and 3.5, and its cleavage can also be two perfect prismatic on 110.
Pronouncing Hornblende can be tricky because the “e” is silent. You can break it down into two words (Horn-Blend) and then run them together when you say Hornblende.