MOLYBDENITE, M-450. Australia. 3/4 to 1-1/2 inch xls.
pure, no matrix or contaminate.  Average 6 to 12 grams per xl., sold
by weight or individual sample.   

MONTEBRASITE, M-455. South
Dakota. Nearly white cleavage masses. SL CHeck.

MONTICELLITE, M-460.  California.
Light olive green, compact, fine grained crystalline
masses. SL Check.

MONTMORILLONITE (BENTONITE), M-465
South Dakota. Gray clay masses - gravel size 
lumps. Because it decrepitates in the atmosphere, it is
packaged in individual plastic bags in sizes equivalent to
listed sizes. Check for availability. 

MUSCOVITE, M-470.South Dakota.
Silvery, vitreous mica cleavage books around 1" and
1/4 to 1/2 inch thick.  


NEPHELINE, NEPHELITE, M-480. 
Canada. Light gray. Greasy luster. 

OLIGOCLASE, M-485. Canada. White
cleavages some with twinning striae. Check for availability.

OLIVINE, M-490 North Carolina, Light
to medium grass green or olive green, sugary crystalline
masses. 

OLIVINE, M-490A. Washington.
Granular to coarse crystalline, grayish green,
some interrupted cleavage faces. Near Forsterite
end of series. Check.

OPAL, Opalite, M-495. 
California. Light gray, red, brown and
green, etc. Pearly to resinous common
opal. 

OPAL (DIATOMITE, DIATOMACEOUS
EARTH), M-500. California or Nevada. White
to light grayish, friable, earthy masses.  

ORPIMENT, M- 505. Sold by weight. Nevada.
Pure yellow xls with minor surface alteration. Xls sizes 2cm to almost 6cm.

ORPIMENT, M-505A.  Nevada.  Bright yellow with associated realgar.

ORTHOCLASE CRYSTALS, M-507.  Nevada.  Excellent crystal samples

of this mineral.  Beige to pink to brown crystals averaging 1 inch in size.  Check. 

ORTHOCLASE - For other "Orthoclase" or Potassium feldspar, or K-Spar, see Microcline.

PHLOGOPITE MICA, M-510. 
Canada. Bronze to black cleavage book.  SL

PIRSSONITE, M-515. California. About
8 - 10 crystals about 1/4 inch (orthorhombic, translucent, gray)
 in a plastic envelope. Check

PLAGIOCLASE, see under ALBITE, ANDESINE,
ANORTHITE, LABRADORITE, OLIGOCLASE.

PLUMBOJAROSITE, M-520. Mexico.
Yellow-brown, earthy lumps and powder in
1 ounce bag. Check.

POTASH ALUM, M-525. Utah. Colorless
to buff groups of 2-30 mm octahedral
crystals. Around 3/4 inch to 1 inch pieces
available.  Check.  SL

PROBERTITE. M-530. California
Colorless, glassy, acicular crystalline
masses. Some with radial structure. SL