Machatschkiite is a rare calcium arsenate, typically colorless. It is a very rare secondary mineral in crusts on granite. Associated minerals include picropharmacolite, pharmacolite and gypsum. It was first described from Anton mine, Heubachtal, near Schiltach, Black Forest, Germany.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Machatschkiite

Hardness: 2-3
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this machatschkiite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch machatschkiite with a known reference. Machatschkiite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Machatschkiite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Machatschkiite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: tabular crystals.

Often confused with

Machatschkiite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Mixite

Mohs 3-4

How to tell apart: Streak differs, so Machatschkiite leaves white, Mixite leaves pale bluish green.

How to tell apart: Cornwallite is the harder of the two (Mohs 4.5 vs. 2-3); streak differs, so Machatschkiite leaves white, Cornwallite leaves pale green.

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Often found alongside machatschkiite

Minerals reported to co-occur with machatschkiite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Ca₆(AsO₄)(AsO₃OH)₃(PO₄)(H₂O)₁₂·3H₂O
Mohs hardness: 2-3
Density: 2.5-2.6 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Tabular Crystals
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Oxidized Hydrothermal Deposits

Where rockhounds find machatschkiite

Classic worldwide localities

Anton mine, Black Forest, Germany

Field-hunting tip

Look in oxidized hydrothermal deposits country, the host setting where machatschkiite typically forms. If you start seeing tennantite, azurite, brochantite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify machatschkiite?+

Mohs hardness is 2-3. It typically shows a vitreous luster. The streak is white. Common colors include colorless.

Where is machatschkiite found?+

Notable localities include Anton mine, Black Forest, Germany.

Is machatschkiite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like machatschkiite?+

Machatschkiite is most often confused with Mixite, Cornwallite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with machatschkiite?+

Machatschkiite commonly co-occurs with Tennantite, Azurite, Brochantite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does machatschkiite form in?+

Machatschkiite typically forms in oxidized hydrothermal deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is machatschkiite used for?+

Machatschkiite is used in collector.

Find machatschkiite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.