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Firstly, this Harlequin Mosaic Pattern is just delightful. In fact, the pattern is simply created by combining slip stitches with knit stitches.
As this mosaic pattern is a slip-stitch, color-change pattern, you are working with just one color per row. This makes it perfect for knitters who want to knit with more than one color without having to learn stranded or fair-isle knitting.
The result is a beautiful pattern of contrasting diamonds that have a nubby garter-stitch texture.
Conversely, you can also give the diamond pattern a smooth texture. In fact, this can be achieved by just purling all the wrong-side (WS) rows.
Either way, this Harlequin mosaic pattern is perfect for socks, knitted vests, ties, and more.
Finally, we have a great step-by-step tutorial about slipping stitches that you can find here: Slipping Stitches Knitwise or Purlwise
In addition, you may also find this article on mosaic knitting interesting: All You Need to Know About Mosaic Knitting..

Techniques Needed for Harlequin Mosaic Pattern
Abbreviation Description Tutorial
k knit Knit Stitch Continental Style
Knit Stitch English Style
p purl Purl Stitch Continental Style
Purl Stitch English Style
Other Abbreviations Used
ws wrong side
rs right side
rep repeat
st(s) stitch(es)
wyif with yarn in front
wyib with yarn in back
Instructions (Knitted Flat)
Multiple of 10 sts plus 3. Colors A and B. Cast on with Color A and knit one row.
Note: On RS (odd-numbered) rows slip all sl-sts with yarn in back.
Row 1 (RS): With B, k1, * sl 1, k9; rep from *, end sl 1, k1.
Row 2: Using same color as Row 1, repeat Row 1, but slip all sl-sts with yarn in front.
Row 3: With A, k3, * (sl 1, k1) 3 times, sl 1, k3; rep from *.
Row 4: Using same color as Row 3, repeat Row 3, but slip all sl-sts with yarn in front.
Row 5: With B, k2, * sl 1, k7, sl 1, k1; rep from *, end k1.
Row 6: Using same color as Row 5, repeat Row 5, but slip all sl-sts with yarn in front.
Row 7: With A, k4, * (sl 1, k1) twice, sl 1, k5; rep from *, end last repeat k4.
Row 8: Using same color as Row 7, repeat Row 7, but slip all sl-sts with yarn in front.
Row 9: With B, (k1, sl 1) twice, * k5, (sl 1, k1) twice, sl 1; rep from *, end k5 (sl 1, k1) twice.
Row 10: Using same color as Row 9, repeat Row 9, but slip all sl-sts with yarn in front.
Row 11: With A, k5, * sl 1, k1, sl 1, k7; rep from *, end last repeat k5.
Row 12: Using same color as Row 11, repeat Row 11, but slip all sl-sts with yarn in front.
Row 13: With B, k1, (k1, sl 1) twice, * k3, (sl 1, k1) 3 times, sl 1; rep from *, end k3, (sl 1, k1) twice, k1
Row 14: Using same color as Row 13, repeat Row 13, but slip all sl-sts with yarn in front
Row 15: With A, k6, * sl 1, k9; rep from *, end last repeat k6
Row 16: Using same color as Row 15, repeat Row 15, but slip all sl-sts with yarn in front
Row 17: With B, repeat Rows 13 and 14
Row 18: With B, repeat Rows 13 and 14
Row 19: With A, repeat Rows 11 and 12
Row 20: With A, repeat Rows 11 and 12
Row 21: With B, repeat Rows 9 and 10
Row 22: With B, repeat Rows 9 and 10
Row 23: With A, repeat Rows 7 and 8
Row 24: With A, repeat Rows 7 and 8
Row 25: With B, repeat Rows 5 and 6
Row 26: With B, repeat Rows 5 and 6
Row 27: With A, repeat Rows 3 and 4
Row 28: With A, repeat Rows 3 and 4
Repeat Rows 1-28 until you have reached your desired length.